diff --git a/drivers/irqchip/irq-realtek-rtl.c b/drivers/irqchip/irq-realtek-rtl.c
index 160feae0ded7..2a349082af81 100644
--- a/drivers/irqchip/irq-realtek-rtl.c
+++ b/drivers/irqchip/irq-realtek-rtl.c
@@ -21,11 +21,33 @@
 #define RTL_ICTL_IRR2		0x10
 #define RTL_ICTL_IRR3		0x14
 
+#define RTL_ICTL_NUM_INPUTS	32
+
 #define REG(x)		(realtek_ictl_base + x)
 
 static DEFINE_RAW_SPINLOCK(irq_lock);
 static void __iomem *realtek_ictl_base;
 
+/*
+ * IRR0-IRR3 store 4 bits per interrupt, but Realtek uses inverted numbering,
+ * placing IRQ 31 in the first four bits. A routing value of '0' means the
+ * interrupt is left disconnected. Routing values {1..15} connect to output
+ * lines {0..14}.
+ */
+#define IRR_OFFSET(idx)		(4 * (3 - (idx * 4) / 32))
+#define IRR_SHIFT(idx)		((idx * 4) % 32)
+
+static void write_irr(void __iomem *irr0, int idx, u32 value)
+{
+	unsigned int offset = IRR_OFFSET(idx);
+	unsigned int shift = IRR_SHIFT(idx);
+	u32 irr;
+
+	irr = readl(irr0 + offset) & ~(0xf << shift);
+	irr |= (value & 0xf) << shift;
+	writel(irr, irr0 + offset);
+}
+
 static void realtek_ictl_unmask_irq(struct irq_data *i)
 {
 	unsigned long flags;
@@ -62,8 +84,14 @@ static struct irq_chip realtek_ictl_irq = {
 
 static int intc_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw)
 {
+	unsigned long flags;
+
 	irq_set_chip_and_handler(irq, &realtek_ictl_irq, handle_level_irq);
 
+	raw_spin_lock_irqsave(&irq_lock, flags);
+	write_irr(REG(RTL_ICTL_IRR0), hw, 1);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
+
 	return 0;
 }
 
@@ -95,89 +123,50 @@ static void realtek_irq_dispatch(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
-/*
- * SoC interrupts are cascaded to MIPS CPU interrupts according to the
- * interrupt-map in the device tree. Each SoC interrupt gets 4 bits for
- * the CPU interrupt in an Interrupt Routing Register. Max 32 SoC interrupts
- * thus go into 4 IRRs. A routing value of '0' means the interrupt is left
- * disconnected. Routing values {1..15} connect to output lines {0..14}.
- */
-static int __init map_interrupts(struct device_node *node, struct irq_domain *domain)
-{
-	struct device_node *cpu_ictl;
-	const __be32 *imap;
-	u32 imaplen, soc_int, cpu_int, tmp, regs[4];
-	int ret, i, irr_regs[] = {
-		RTL_ICTL_IRR3,
-		RTL_ICTL_IRR2,
-		RTL_ICTL_IRR1,
-		RTL_ICTL_IRR0,
-	};
-	u8 mips_irqs_set;
-
-	ret = of_property_read_u32(node, "#address-cells", &tmp);
-	if (ret || tmp)
-		return -EINVAL;
-
-	imap = of_get_property(node, "interrupt-map", &imaplen);
-	if (!imap || imaplen % 3)
-		return -EINVAL;
-
-	mips_irqs_set = 0;
-	memset(regs, 0, sizeof(regs));
-	for (i = 0; i < imaplen; i += 3 * sizeof(u32)) {
-		soc_int = be32_to_cpup(imap);
-		if (soc_int > 31)
-			return -EINVAL;
-
-		cpu_ictl = of_find_node_by_phandle(be32_to_cpup(imap + 1));
-		if (!cpu_ictl)
-			return -EINVAL;
-		ret = of_property_read_u32(cpu_ictl, "#interrupt-cells", &tmp);
-		of_node_put(cpu_ictl);
-		if (ret || tmp != 1)
-			return -EINVAL;
-
-		cpu_int = be32_to_cpup(imap + 2);
-		if (cpu_int > 7 || cpu_int < 2)
-			return -EINVAL;
-
-		if (!(mips_irqs_set & BIT(cpu_int))) {
-			irq_set_chained_handler_and_data(cpu_int, realtek_irq_dispatch,
-							 domain);
-			mips_irqs_set |= BIT(cpu_int);
-		}
-
-		/* Use routing values (1..6) for CPU interrupts (2..7) */
-		regs[(soc_int * 4) / 32] |= (cpu_int - 1) << (soc_int * 4) % 32;
-		imap += 3;
-	}
-
-	for (i = 0; i < 4; i++)
-		writel(regs[i], REG(irr_regs[i]));
-
-	return 0;
-}
-
 static int __init realtek_rtl_of_init(struct device_node *node, struct device_node *parent)
 {
+	struct of_phandle_args oirq;
 	struct irq_domain *domain;
-	int ret;
+	unsigned int soc_irq;
+	int parent_irq;
 
 	realtek_ictl_base = of_iomap(node, 0);
 	if (!realtek_ictl_base)
 		return -ENXIO;
 
-	/* Disable all cascaded interrupts */
+	/* Disable all cascaded interrupts and clear routing */
 	writel(0, REG(RTL_ICTL_GIMR));
+	for (soc_irq = 0; soc_irq < RTL_ICTL_NUM_INPUTS; soc_irq++)
+		write_irr(REG(RTL_ICTL_IRR0), soc_irq, 0);
+
+	if (WARN_ON(!of_irq_count(node))) {
+		/*
+		 * If DT contains no parent interrupts, assume MIPS CPU IRQ 2
+		 * (HW0) is connected to the first output. This is the case for
+		 * all known hardware anyway. "interrupt-map" is deprecated, so
+		 * don't bother trying to parse that.
+		 */
+		oirq.np = of_find_compatible_node(NULL, NULL, "mti,cpu-interrupt-controller");
+		oirq.args_count = 1;
+		oirq.args[0] = 2;
+
+		parent_irq = irq_create_of_mapping(&oirq);
+
+		of_node_put(oirq.np);
+	} else {
+		parent_irq = of_irq_get(node, 0);
+	}
 
-	domain = irq_domain_add_linear(node, 32, &irq_domain_ops, NULL);
+	if (parent_irq < 0)
+		return parent_irq;
+	else if (!parent_irq)
+		return -ENODEV;
 
-	ret = map_interrupts(node, domain);
-	if (ret) {
-		pr_err("invalid interrupt map\n");
-		return ret;
-	}
+	domain = irq_domain_add_linear(node, RTL_ICTL_NUM_INPUTS, &irq_domain_ops, NULL);
+	if (!domain)
+		return -ENOMEM;
+
+	irq_set_chained_handler_and_data(parent_irq, realtek_irq_dispatch, domain);
 
 	return 0;
 }
