MIPS: JZ4740: parse SoC interrupt controller parent IRQ from DT

Rather than hardcoding the IRQ number used to cascade interrupts from
the SoC interrupt controller to the CPU interrupt controller, read that
IRQ number from the DT describing the system.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: Brian Norris <computersforpeace@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/10137/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/jz4740/irq.c

@@ -85,6 +85,11 @@ static int __init jz4740_intc_of_init(struct device_node *node,
 {
 	struct irq_chip_generic *gc;
 	struct irq_chip_type *ct;
+	int parent_irq;
+
+	parent_irq = irq_of_parse_and_map(node, 0);
+	if (!parent_irq)
+		return -EINVAL;
 
 	jz_intc_base = ioremap(JZ4740_INTC_BASE_ADDR, 0x14);
 
@@ -108,7 +113,7 @@ static int __init jz4740_intc_of_init(struct device_node *node,
 
 	irq_setup_generic_chip(gc, IRQ_MSK(32), 0, 0, IRQ_NOPROBE | IRQ_LEVEL);
 
-	setup_irq(2, &jz4740_cascade_action);
+	setup_irq(parent_irq, &jz4740_cascade_action);
 	return 0;
 }
 IRQCHIP_DECLARE(jz4740_intc, "ingenic,jz4740-intc", jz4740_intc_of_init);