diff --git a/drivers/platform/Kconfig b/drivers/platform/Kconfig
index b437847b6237..5f8b9bcdb830 100644
--- a/drivers/platform/Kconfig
+++ b/drivers/platform/Kconfig
@@ -13,4 +13,6 @@ source "drivers/platform/olpc/Kconfig"
 
 source "drivers/platform/surface/Kconfig"
 
+source "drivers/platform/apple/Kconfig"
+
 source "drivers/platform/x86/Kconfig"
diff --git a/drivers/platform/Makefile b/drivers/platform/Makefile
index 4de08ef4ec9d..3e5d5039a28c 100644
--- a/drivers/platform/Makefile
+++ b/drivers/platform/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_OLPC_EC)		+= olpc/
 obj-$(CONFIG_GOLDFISH)		+= goldfish/
 obj-$(CONFIG_CHROME_PLATFORMS)	+= chrome/
 obj-$(CONFIG_SURFACE_PLATFORMS)	+= surface/
+obj-$(CONFIG_APPLE_PLATFORMS)	+= apple/
diff --git a/drivers/platform/apple/Kconfig b/drivers/platform/apple/Kconfig
new file mode 100644
index 000000000000..42525aa9fbbe
--- /dev/null
+++ b/drivers/platform/apple/Kconfig
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Apple Platform-Specific Drivers
+#
+
+menuconfig APPLE_PLATFORMS
+	bool "Apple Mac Platform-Specific Device Drivers"
+	default y
+	help
+	  Say Y here to get to see options for platform-specific device drivers
+	  for Apple devices. This option alone does not add any kernel code.
+
+	  If you say N, all options in this submenu will be skipped and disabled.
+
+if APPLE_PLATFORMS
+
+config APPLE_SMC
+	tristate "Apple SMC Driver"
+	depends on ARCH_APPLE || COMPILE_TEST
+	default ARCH_APPLE
+	select MFD_CORE
+	help
+	  Build support for the Apple System Management Controller present in
+	  Apple Macs. This driver currently supports the SMC in Apple Silicon
+	  Macs. For x86 Macs, see the applesmc driver (SENSORS_APPLESMC).
+
+	  Say Y here if you have an Apple Silicon Mac.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called macsmc.
+
+if APPLE_SMC
+
+config APPLE_SMC_RTKIT
+	tristate "RTKit (Apple Silicon) backend"
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on APPLE_RTKIT
+	default ARCH_APPLE
+	help
+	  Build support for SMC communications via the RTKit backend. This is
+	  required for Apple Silicon Macs.
+
+	  Say Y here if you have an Apple Silicon Mac.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called macsmc-rtkit.
+
+endif
+endif
diff --git a/drivers/platform/apple/Makefile b/drivers/platform/apple/Makefile
new file mode 100644
index 000000000000..79fac195398b
--- /dev/null
+++ b/drivers/platform/apple/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for linux/drivers/platform/apple
+# Apple Platform-Specific Drivers
+#
+
+macsmc-y				+= smc_core.o
+macsmc-rtkit-y				+= smc_rtkit.o
+
+obj-$(CONFIG_APPLE_SMC)			+= macsmc.o
+obj-$(CONFIG_APPLE_SMC_RTKIT)		+= macsmc-rtkit.o
diff --git a/drivers/platform/apple/smc.h b/drivers/platform/apple/smc.h
new file mode 100644
index 000000000000..8ae51887b2c5
--- /dev/null
+++ b/drivers/platform/apple/smc.h
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC internal core definitions
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#ifndef _SMC_H
+#define _SMC_H
+
+#include <linux/mfd/macsmc.h>
+
+struct apple_smc_backend_ops {
+	int (*read_key)(void *cookie, smc_key key, void *buf, size_t size);
+	int (*write_key)(void *cookie, smc_key key, void *buf, size_t size);
+	int (*write_key_atomic)(void *cookie, smc_key key, void *buf, size_t size);
+	int (*rw_key)(void *cookie, smc_key key, void *wbuf, size_t wsize,
+		      void *rbuf, size_t rsize);
+	int (*get_key_by_index)(void *cookie, int index, smc_key *key);
+	int (*get_key_info)(void *cookie, smc_key key, struct apple_smc_key_info *info);
+};
+
+struct apple_smc *apple_smc_probe(struct device *dev, const struct apple_smc_backend_ops *ops,
+				  void *cookie);
+void *apple_smc_get_cookie(struct apple_smc *smc);
+int apple_smc_remove(struct apple_smc *smc);
+void apple_smc_event_received(struct apple_smc *smc, uint32_t event);
+
+#endif
diff --git a/drivers/platform/apple/smc_core.c b/drivers/platform/apple/smc_core.c
new file mode 100644
index 000000000000..daf029cd072f
--- /dev/null
+++ b/drivers/platform/apple/smc_core.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC core framework
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/device.h>
+#include <linux/mfd/core.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include "smc.h"
+
+struct apple_smc {
+	struct device *dev;
+
+	void *be_cookie;
+	const struct apple_smc_backend_ops *be;
+
+	struct mutex mutex;
+
+	u32 key_count;
+	smc_key first_key;
+	smc_key last_key;
+
+	struct blocking_notifier_head event_handlers;
+};
+
+static const struct mfd_cell apple_smc_devs[] = {
+	{
+		.name = "macsmc-gpio",
+	},
+	{
+		.name = "macsmc-hid",
+	},
+	{
+		.name = "macsmc-power",
+	},
+	{
+		.name = "macsmc-reboot",
+	},
+	{
+		.name = "macsmc-rtc",
+	},
+};
+
+int apple_smc_read(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	int ret;
+
+	mutex_lock(&smc->mutex);
+	ret = smc->be->read_key(smc->be_cookie, key, buf, size);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_read);
+
+int apple_smc_write(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	int ret;
+
+	mutex_lock(&smc->mutex);
+	ret = smc->be->write_key(smc->be_cookie, key, buf, size);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_write);
+
+int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	int ret;
+
+	/*
+	 * Will fail if SMC is busy. This is only used by SMC reboot/poweroff
+	 * final calls, so it doesn't really matter at that point.
+	 */
+	if (!mutex_trylock(&smc->mutex))
+		return -EBUSY;
+
+	ret = smc->be->write_key_atomic(smc->be_cookie, key, buf, size);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_write_atomic);
+
+int apple_smc_rw(struct apple_smc *smc, smc_key key, void *wbuf, size_t wsize,
+		 void *rbuf, size_t rsize)
+{
+	int ret;
+
+	mutex_lock(&smc->mutex);
+	ret = smc->be->rw_key(smc->be_cookie, key, wbuf, wsize, rbuf, rsize);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_rw);
+
+int apple_smc_get_key_by_index(struct apple_smc *smc, int index, smc_key *key)
+{
+	int ret;
+
+	mutex_lock(&smc->mutex);
+	ret = smc->be->get_key_by_index(smc->be_cookie, index, key);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_get_key_by_index);
+
+int apple_smc_get_key_info(struct apple_smc *smc, smc_key key, struct apple_smc_key_info *info)
+{
+	int ret;
+
+	mutex_lock(&smc->mutex);
+	ret = smc->be->get_key_info(smc->be_cookie, key, info);
+	mutex_unlock(&smc->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_get_key_info);
+
+int apple_smc_find_first_key_index(struct apple_smc *smc, smc_key key)
+{
+	int start = 0, count = smc->key_count;
+	int ret;
+
+	if (key <= smc->first_key)
+		return 0;
+	if (key > smc->last_key)
+		return smc->key_count;
+
+	while (count > 1) {
+		int pivot = start + ((count - 1) >> 1);
+		smc_key pkey;
+
+		ret = apple_smc_get_key_by_index(smc, pivot, &pkey);
+		if (ret < 0)
+			return ret;
+
+		if (pkey == key)
+			return pivot;
+
+		pivot++;
+
+		if (pkey < key) {
+			count -= pivot - start;
+			start = pivot;
+		} else {
+			count = pivot - start;
+		}
+	}
+
+	return start;
+}
+EXPORT_SYMBOL(apple_smc_find_first_key_index);
+
+int apple_smc_get_key_count(struct apple_smc *smc)
+{
+	return smc->key_count;
+}
+EXPORT_SYMBOL(apple_smc_get_key_count);
+
+void apple_smc_event_received(struct apple_smc *smc, uint32_t event)
+{
+	dev_dbg(smc->dev, "Event: 0x%08x\n", event);
+	blocking_notifier_call_chain(&smc->event_handlers, event, NULL);
+}
+EXPORT_SYMBOL(apple_smc_event_received);
+
+int apple_smc_register_notifier(struct apple_smc *smc, struct notifier_block *n)
+{
+	return blocking_notifier_chain_register(&smc->event_handlers, n);
+}
+EXPORT_SYMBOL(apple_smc_register_notifier);
+
+int apple_smc_unregister_notifier(struct apple_smc *smc, struct notifier_block *n)
+{
+	return blocking_notifier_chain_unregister(&smc->event_handlers, n);
+}
+EXPORT_SYMBOL(apple_smc_unregister_notifier);
+
+void *apple_smc_get_cookie(struct apple_smc *smc)
+{
+	return smc->be_cookie;
+}
+EXPORT_SYMBOL(apple_smc_get_cookie);
+
+struct apple_smc *apple_smc_probe(struct device *dev, const struct apple_smc_backend_ops *ops, void *cookie)
+{
+	struct apple_smc *smc;
+	u32 count;
+	int ret;
+
+	smc = devm_kzalloc(dev, sizeof(*smc), GFP_KERNEL);
+	if (!smc)
+		return ERR_PTR(-ENOMEM);
+
+	smc->dev = dev;
+	smc->be_cookie = cookie;
+	smc->be = ops;
+	mutex_init(&smc->mutex);
+	BLOCKING_INIT_NOTIFIER_HEAD(&smc->event_handlers);
+
+	ret = apple_smc_read_u32(smc, SMC_KEY(#KEY), &count);
+	if (ret)
+		return ERR_PTR(dev_err_probe(dev, ret, "Failed to get key count"));
+	smc->key_count = be32_to_cpu(count);
+
+	ret = apple_smc_get_key_by_index(smc, 0, &smc->first_key);
+	if (ret)
+		return ERR_PTR(dev_err_probe(dev, ret, "Failed to get first key"));
+
+	ret = apple_smc_get_key_by_index(smc, smc->key_count - 1, &smc->last_key);
+	if (ret)
+		return ERR_PTR(dev_err_probe(dev, ret, "Failed to get last key"));
+
+	/* Enable notifications */
+	apple_smc_write_flag(smc, SMC_KEY(NTAP), 1);
+
+	dev_info(dev, "Initialized (%d keys %p4ch..%p4ch)\n",
+		 smc->key_count, &smc->first_key, &smc->last_key);
+
+	dev_set_drvdata(dev, smc);
+
+	ret = mfd_add_devices(dev, -1, apple_smc_devs, ARRAY_SIZE(apple_smc_devs), NULL, 0, NULL);
+	if (ret)
+		return ERR_PTR(dev_err_probe(dev, ret, "Subdevice initialization failed"));
+
+	return smc;
+}
+EXPORT_SYMBOL(apple_smc_probe);
+
+int apple_smc_remove(struct apple_smc *smc)
+{
+	mfd_remove_devices(smc->dev);
+
+	/* Disable notifications */
+	apple_smc_write_flag(smc, SMC_KEY(NTAP), 1);
+
+	return 0;
+}
+EXPORT_SYMBOL(apple_smc_remove);
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC core");
diff --git a/drivers/platform/apple/smc_rtkit.c b/drivers/platform/apple/smc_rtkit.c
new file mode 100644
index 000000000000..5b7c4c475bbb
--- /dev/null
+++ b/drivers/platform/apple/smc_rtkit.c
@@ -0,0 +1,451 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC RTKit backend
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <asm/unaligned.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/soc/apple/rtkit.h>
+#include "smc.h"
+
+#define SMC_ENDPOINT			0x20
+
+/* Guess */
+#define SMC_SHMEM_SIZE			0x1000
+
+#define SMC_MSG_READ_KEY		0x10
+#define SMC_MSG_WRITE_KEY		0x11
+#define SMC_MSG_GET_KEY_BY_INDEX	0x12
+#define SMC_MSG_GET_KEY_INFO		0x13
+#define SMC_MSG_INITIALIZE		0x17
+#define SMC_MSG_NOTIFICATION		0x18
+#define SMC_MSG_RW_KEY			0x20
+
+#define SMC_DATA			GENMASK(63, 32)
+#define SMC_WSIZE			GENMASK(31, 24)
+#define SMC_SIZE			GENMASK(23, 16)
+#define SMC_ID				GENMASK(15, 12)
+#define SMC_MSG				GENMASK(7, 0)
+#define SMC_RESULT			SMC_MSG
+
+#define SMC_RECV_TIMEOUT		100
+
+struct apple_smc_rtkit {
+	struct device *dev;
+	struct apple_smc *core;
+	struct apple_rtkit *rtk;
+
+	struct completion init_done;
+	bool initialized;
+	bool alive;
+
+	struct resource *sram;
+	void __iomem *sram_base;
+	struct apple_rtkit_shmem shmem;
+
+	unsigned int msg_id;
+
+	bool atomic_pending;
+	struct completion cmd_done;
+	u64 cmd_ret;
+};
+
+static int apple_smc_rtkit_write_key_atomic(void *cookie, smc_key key, void *buf, size_t size)
+{
+	struct apple_smc_rtkit *smc = cookie;
+	int ret;
+	u64 msg;
+	u8 result;
+
+	if (size > SMC_SHMEM_SIZE || size == 0)
+		return -EINVAL;
+
+	if (!smc->alive)
+		return -EIO;
+
+	memcpy_toio(smc->shmem.iomem, buf, size);
+	smc->msg_id = (smc->msg_id + 1) & 0xf;
+	msg = (FIELD_PREP(SMC_MSG, SMC_MSG_WRITE_KEY) |
+	       FIELD_PREP(SMC_SIZE, size) |
+	       FIELD_PREP(SMC_ID, smc->msg_id) |
+	       FIELD_PREP(SMC_DATA, key));
+	smc->atomic_pending = true;
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT, msg, NULL, true);
+	if (ret < 0) {
+		dev_err(smc->dev, "Failed to send command (%d)\n", ret);
+		return ret;
+	}
+
+	while (smc->atomic_pending) {
+		ret = apple_rtkit_poll(smc->rtk);
+		if (ret < 0) {
+			dev_err(smc->dev, "RTKit poll failed (%llx)", msg);
+			return ret;
+		}
+		udelay(100);
+	}
+
+	if (FIELD_GET(SMC_ID, smc->cmd_ret) != smc->msg_id) {
+		dev_err(smc->dev, "Command sequence mismatch (expected %d, got %d)\n",
+			smc->msg_id, (unsigned int)FIELD_GET(SMC_ID, smc->cmd_ret));
+		return -EIO;
+	}
+
+	result = FIELD_GET(SMC_RESULT, smc->cmd_ret);
+	if (result != 0)
+		return -result;
+
+	return FIELD_GET(SMC_SIZE, smc->cmd_ret);
+}
+
+static int apple_smc_cmd(struct apple_smc_rtkit *smc, u64 cmd, u64 arg,
+			 u64 size, u64 wsize, u32 *ret_data)
+{
+	int ret;
+	u64 msg;
+	u8 result;
+
+	if (!smc->alive)
+		return -EIO;
+
+	reinit_completion(&smc->cmd_done);
+
+	smc->msg_id = (smc->msg_id + 1) & 0xf;
+	msg = (FIELD_PREP(SMC_MSG, cmd) |
+	       FIELD_PREP(SMC_SIZE, size) |
+	       FIELD_PREP(SMC_WSIZE, wsize) |
+	       FIELD_PREP(SMC_ID, smc->msg_id) |
+	       FIELD_PREP(SMC_DATA, arg));
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT, msg, NULL, false);
+	if (ret < 0) {
+		dev_err(smc->dev, "Failed to send command\n");
+		return ret;
+	}
+
+	do {
+		if (wait_for_completion_timeout(&smc->cmd_done,
+						msecs_to_jiffies(SMC_RECV_TIMEOUT)) == 0) {
+			dev_err(smc->dev, "Command timed out (%llx)", msg);
+			return -ETIMEDOUT;
+		}
+		if (FIELD_GET(SMC_ID, smc->cmd_ret) == smc->msg_id)
+			break;
+		dev_err(smc->dev, "Command sequence mismatch (expected %d, got %d)\n",
+			smc->msg_id, (unsigned int)FIELD_GET(SMC_ID, smc->cmd_ret));
+	} while(1);
+
+	result = FIELD_GET(SMC_RESULT, smc->cmd_ret);
+	if (result != 0)
+		return -result;
+
+	if (ret_data)
+		*ret_data = FIELD_GET(SMC_DATA, smc->cmd_ret);
+
+	return FIELD_GET(SMC_SIZE, smc->cmd_ret);
+}
+
+static int _apple_smc_rtkit_read_key(struct apple_smc_rtkit *smc, smc_key key,
+				     void *buf, size_t size, size_t wsize)
+{
+	int ret;
+	u32 rdata;
+	u64 cmd;
+
+	if (size > SMC_SHMEM_SIZE || size == 0)
+		return -EINVAL;
+
+	cmd = wsize ? SMC_MSG_RW_KEY : SMC_MSG_READ_KEY;
+
+	ret = apple_smc_cmd(smc, cmd, key, size, wsize, &rdata);
+	if (ret < 0)
+		return ret;
+
+	if (size <= 4)
+		memcpy(buf, &rdata, size);
+	else
+		memcpy_fromio(buf, smc->shmem.iomem, size);
+
+	return ret;
+}
+
+static int apple_smc_rtkit_read_key(void *cookie, smc_key key, void *buf, size_t size)
+{
+	return _apple_smc_rtkit_read_key(cookie, key, buf, size, 0);
+}
+
+static int apple_smc_rtkit_write_key(void *cookie, smc_key key, void *buf, size_t size)
+{
+	struct apple_smc_rtkit *smc = cookie;
+
+	if (size > SMC_SHMEM_SIZE || size == 0)
+		return -EINVAL;
+
+	memcpy_toio(smc->shmem.iomem, buf, size);
+	return apple_smc_cmd(smc, SMC_MSG_WRITE_KEY, key, size, 0, NULL);
+}
+
+static int apple_smc_rtkit_rw_key(void *cookie, smc_key key,
+				  void *wbuf, size_t wsize, void *rbuf, size_t rsize)
+{
+	struct apple_smc_rtkit *smc = cookie;
+
+	if (wsize > SMC_SHMEM_SIZE || wsize == 0)
+		return -EINVAL;
+
+	memcpy_toio(smc->shmem.iomem, wbuf, wsize);
+	return _apple_smc_rtkit_read_key(smc, key, rbuf, rsize, wsize);
+}
+
+static int apple_smc_rtkit_get_key_by_index(void *cookie, int index, smc_key *key)
+{
+	struct apple_smc_rtkit *smc = cookie;
+	int ret;
+
+	ret = apple_smc_cmd(smc, SMC_MSG_GET_KEY_BY_INDEX, index, 0, 0, key);
+
+	*key = swab32(*key);
+	return ret;
+}
+
+static int apple_smc_rtkit_get_key_info(void *cookie, smc_key key, struct apple_smc_key_info *info)
+{
+	struct apple_smc_rtkit *smc = cookie;
+	u8 key_info[6];
+	int ret;
+
+	ret = apple_smc_cmd(smc, SMC_MSG_GET_KEY_INFO, key, 0, 0, NULL);
+	if (ret >= 0 && info) {
+		info->size = key_info[0];
+		info->type_code = get_unaligned_be32(&key_info[1]);
+		info->flags = key_info[5];
+	}
+	return ret;
+}
+
+static const struct apple_smc_backend_ops apple_smc_rtkit_be_ops = {
+	.read_key = apple_smc_rtkit_read_key,
+	.write_key = apple_smc_rtkit_write_key,
+	.write_key_atomic = apple_smc_rtkit_write_key_atomic,
+	.rw_key = apple_smc_rtkit_rw_key,
+	.get_key_by_index = apple_smc_rtkit_get_key_by_index,
+	.get_key_info = apple_smc_rtkit_get_key_info,
+};
+
+static void apple_smc_rtkit_crashed(void *cookie)
+{
+	struct apple_smc_rtkit *smc = cookie;
+
+	dev_err(smc->dev, "SMC crashed! Your system will reboot in a few seconds...\n");
+	smc->alive = false;
+}
+
+static int apple_smc_rtkit_shmem_setup(void *cookie, struct apple_rtkit_shmem *bfr)
+{
+	struct apple_smc_rtkit *smc = cookie;
+	struct resource res = {
+		.start = bfr->iova,
+		.end = bfr->iova + bfr->size - 1,
+		.name = "rtkit_map",
+		.flags = smc->sram->flags,
+	};
+
+	if (!bfr->iova) {
+		dev_err(smc->dev, "RTKit wants a RAM buffer\n");
+		return -EIO;
+	}
+
+	if (res.end < res.start || !resource_contains(smc->sram, &res)) {
+		dev_err(smc->dev,
+			"RTKit buffer request outside SRAM region: %pR", &res);
+		return -EFAULT;
+	}
+
+	bfr->iomem = smc->sram_base + (res.start - smc->sram->start);
+	bfr->is_mapped = true;
+
+	return 0;
+}
+
+static void apple_smc_rtkit_shmem_destroy(void *cookie, struct apple_rtkit_shmem *bfr)
+{
+	// no-op
+}
+
+static bool apple_smc_rtkit_recv_early(void *cookie, u8 endpoint, u64 message)
+{
+	struct apple_smc_rtkit *smc = cookie;
+
+	if (endpoint != SMC_ENDPOINT) {
+		dev_err(smc->dev, "Received message for unknown endpoint 0x%x\n", endpoint);
+		return false;
+	}
+
+	if (!smc->initialized) {
+		int ret;
+
+		smc->shmem.iova = message;
+		smc->shmem.size = SMC_SHMEM_SIZE;
+		ret = apple_smc_rtkit_shmem_setup(smc, &smc->shmem);
+		if (ret < 0)
+			dev_err(smc->dev, "Failed to initialize shared memory\n");
+		else
+			smc->alive = true;
+		smc->initialized = true;
+		complete(&smc->init_done);
+	} else if (FIELD_GET(SMC_MSG, message) == SMC_MSG_NOTIFICATION) {
+		/* Handle these in the RTKit worker thread */
+		return false;
+	} else {
+		smc->cmd_ret = message;
+		if (smc->atomic_pending) {
+			smc->atomic_pending = false;
+		} else {
+			complete(&smc->cmd_done);
+		}
+	}
+
+	return true;
+}
+
+static void apple_smc_rtkit_recv(void *cookie, u8 endpoint, u64 message)
+{
+	struct apple_smc_rtkit *smc = cookie;
+
+	if (endpoint != SMC_ENDPOINT) {
+		dev_err(smc->dev, "Received message for unknown endpoint 0x%x\n", endpoint);
+		return;
+	}
+
+	if (FIELD_GET(SMC_MSG, message) != SMC_MSG_NOTIFICATION) {
+		dev_err(smc->dev, "Received unknown message from worker: 0x%llx\n", message);
+		return;
+	}
+
+	apple_smc_event_received(smc->core, FIELD_GET(SMC_DATA, message));
+}
+
+static const struct apple_rtkit_ops apple_smc_rtkit_ops = {
+	.crashed = apple_smc_rtkit_crashed,
+	.recv_message = apple_smc_rtkit_recv,
+	.recv_message_early = apple_smc_rtkit_recv_early,
+	.shmem_setup = apple_smc_rtkit_shmem_setup,
+	.shmem_destroy = apple_smc_rtkit_shmem_destroy,
+};
+
+static int apple_smc_rtkit_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct apple_smc_rtkit *smc;
+	int ret;
+
+	smc = devm_kzalloc(dev, sizeof(*smc), GFP_KERNEL);
+	if (!smc)
+		return -ENOMEM;
+
+	smc->dev = dev;
+
+	smc->sram = platform_get_resource_byname(pdev, IORESOURCE_MEM, "sram");
+	if (!smc->sram)
+		return dev_err_probe(dev, EIO,
+				     "No SRAM region");
+
+	smc->sram_base = devm_ioremap_resource(dev, smc->sram);
+	if (IS_ERR(smc->sram_base))
+		return dev_err_probe(dev, PTR_ERR(smc->sram_base),
+				     "Failed to map SRAM region");
+
+	smc->rtk =
+		devm_apple_rtkit_init(dev, smc, NULL, 0, &apple_smc_rtkit_ops);
+	if (IS_ERR(smc->rtk))
+		return dev_err_probe(dev, PTR_ERR(smc->rtk),
+				     "Failed to intialize RTKit");
+
+	ret = apple_rtkit_wake(smc->rtk);
+	if (ret != 0)
+		return dev_err_probe(dev, ret,
+				     "Failed to wake up SMC");
+
+	ret = apple_rtkit_start_ep(smc->rtk, SMC_ENDPOINT);
+	if (ret != 0) {
+		dev_err(dev, "Failed to start endpoint");
+		goto cleanup;
+	}
+
+	init_completion(&smc->init_done);
+	init_completion(&smc->cmd_done);
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT,
+				       FIELD_PREP(SMC_MSG, SMC_MSG_INITIALIZE), NULL, false);
+	if (ret < 0)
+		return dev_err_probe(dev, ret,
+				     "Failed to send init message");
+
+	if (wait_for_completion_timeout(&smc->init_done,
+					msecs_to_jiffies(SMC_RECV_TIMEOUT)) == 0) {
+		ret = -ETIMEDOUT;
+		dev_err(dev, "Timed out initializing SMC");
+		goto cleanup;
+	}
+
+	if (!smc->alive) {
+		ret = -EIO;
+		goto cleanup;
+	}
+
+	smc->core = apple_smc_probe(dev, &apple_smc_rtkit_be_ops, smc);
+	if (IS_ERR(smc->core)) {
+		ret = PTR_ERR(smc->core);
+		goto cleanup;
+	}
+
+	return 0;
+
+cleanup:
+	/* Try to shut down RTKit, if it's not completely wedged */
+	if (apple_rtkit_is_running(smc->rtk))
+		apple_rtkit_quiesce(smc->rtk);
+
+	return ret;
+}
+
+static int apple_smc_rtkit_remove(struct platform_device *pdev)
+{
+	struct apple_smc *core = platform_get_drvdata(pdev);
+	struct apple_smc_rtkit *smc = apple_smc_get_cookie(core);
+
+	apple_smc_remove(core);
+
+	if (apple_rtkit_is_running(smc->rtk))
+		apple_rtkit_quiesce(smc->rtk);
+
+	return 0;
+}
+
+static const struct of_device_id apple_smc_rtkit_of_match[] = {
+	{ .compatible = "apple,smc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, apple_smc_rtkit_of_match);
+
+static struct platform_driver apple_smc_rtkit_driver = {
+	.driver = {
+		.name = "macsmc-rtkit",
+		.owner = THIS_MODULE,
+		.of_match_table = apple_smc_rtkit_of_match,
+	},
+	.probe = apple_smc_rtkit_probe,
+	.remove = apple_smc_rtkit_remove,
+};
+module_platform_driver(apple_smc_rtkit_driver);
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC RTKit backend driver");
diff --git a/include/linux/mfd/macsmc.h b/include/linux/mfd/macsmc.h
new file mode 100644
index 000000000000..39b4dc4ca881
--- /dev/null
+++ b/include/linux/mfd/macsmc.h
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC core definitions
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#ifndef _LINUX_MFD_MACSMC_H
+#define _LINUX_MFD_MACSMC_H
+
+struct apple_smc;
+
+typedef u32 smc_key;
+
+#define SMC_KEY(s) (smc_key)(_SMC_KEY(#s))
+#define _SMC_KEY(s) (((s)[0] << 24) | ((s)[1] << 16) | ((s)[2] << 8) | (s)[3])
+
+#define APPLE_SMC_READABLE BIT(7)
+#define APPLE_SMC_WRITABLE BIT(6)
+#define APPLE_SMC_FUNCTION BIT(4)
+
+struct apple_smc_key_info {
+	u8 size;
+	u32 type_code;
+	u8 flags;
+};
+
+int apple_smc_read(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+int apple_smc_write(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+int apple_smc_rw(struct apple_smc *smc, smc_key key, void *wbuf, size_t wsize,
+		 void *rbuf, size_t rsize);
+
+int apple_smc_get_key_count(struct apple_smc *smc);
+int apple_smc_find_first_key_index(struct apple_smc *smc, smc_key key);
+int apple_smc_get_key_by_index(struct apple_smc *smc, int index, smc_key *key);
+int apple_smc_get_key_info(struct apple_smc *smc, smc_key key, struct apple_smc_key_info *info);
+
+static inline bool apple_smc_key_exists(struct apple_smc *smc, smc_key key)
+{
+	return apple_smc_get_key_info(smc, key, NULL) >= 0;
+}
+
+#define APPLE_SMC_TYPE_OPS(type) \
+	static inline int apple_smc_read_##type(struct apple_smc *smc, smc_key key, type *p) \
+	{ \
+		int ret = apple_smc_read(smc, key, p, sizeof(*p)); \
+		return (ret < 0) ? ret : ((ret != sizeof(*p)) ? -EINVAL : 0); \
+	} \
+	static inline int apple_smc_write_##type(struct apple_smc *smc, smc_key key, type p) \
+	{ \
+		return apple_smc_write(smc, key, &p, sizeof(p)); \
+	} \
+	static inline int apple_smc_write_##type##_atomic(struct apple_smc *smc, smc_key key, type p) \
+	{ \
+		return apple_smc_write_atomic(smc, key, &p, sizeof(p)); \
+	} \
+	static inline int apple_smc_rw_##type(struct apple_smc *smc, smc_key key, \
+					      type w, type *r) \
+	{ \
+		int ret = apple_smc_rw(smc, key, &w, sizeof(w), r, sizeof(*r)); \
+		return (ret < 0) ? ret : ((ret != sizeof(*r)) ? -EINVAL : 0); \
+	}
+
+APPLE_SMC_TYPE_OPS(u64)
+APPLE_SMC_TYPE_OPS(u32)
+APPLE_SMC_TYPE_OPS(u16)
+APPLE_SMC_TYPE_OPS(u8)
+APPLE_SMC_TYPE_OPS(s64)
+APPLE_SMC_TYPE_OPS(s32)
+APPLE_SMC_TYPE_OPS(s16)
+APPLE_SMC_TYPE_OPS(s8)
+
+static inline int apple_smc_read_flag(struct apple_smc *smc, smc_key key)
+{
+	u8 val;
+	int ret = apple_smc_read_u8(smc, key, &val);
+	if (ret < 0)
+		return ret;
+	return val ? 1 : 0;
+}
+#define apple_smc_write_flag apple_smc_write_u8
+
+int apple_smc_register_notifier(struct apple_smc *smc, struct notifier_block *n);
+int apple_smc_unregister_notifier(struct apple_smc *smc, struct notifier_block *n);
+
+#endif
