devicetree: Add binding for Sigma Designs SMP86xx interrupt controller

This adds a binding for the secondary interrupt controller in
Sigma Designs SMP86xx and SMP87xx chips.

Signed-off-by: Mans Rullgard <[e-mail]>
[ jac: use 'interrupt-controller@XXX' notation in binding doc ]
Acked-by: Rob Herring <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Jason Cooper <[e-mail]>

Documentation/devicetree/bindings/interrupt-controller/sigma,smp8642-intc.txt

···
+Sigma Designs SMP86xx/SMP87xx secondary interrupt controller
+
+Required properties:
+- compatible: should be "sigma,smp8642-intc"
+- reg: physical address of MMIO region
+- ranges: address space mapping of child nodes
+- interrupt-parent: phandle of parent interrupt controller
+- interrupt-controller: boolean
+- #address-cells: should be <1>
+- #size-cells: should be <1>
+
+One child node per control block with properties:
+- reg: address of registers for this control block
+- interrupt-controller: boolean
+- #interrupt-cells: should be <2>, interrupt index and flags per interrupts.txt
+- interrupts: interrupt spec of primary interrupt controller
+
+Example:
+
+interrupt-controller@6e000 {
+	compatible = "sigma,smp8642-intc";
+	reg = <0x6e000 0x400>;
+	ranges = <0x0 0x6e000 0x400>;
+	interrupt-parent = <&gic>;
+	interrupt-controller;
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	irq0: interrupt-controller@0 {
+		reg = <0x000 0x100>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;
+	};
+
+	irq1: interrupt-controller@100 {
+		reg = <0x100 0x100>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
+	};
+
+	irq2: interrupt-controller@300 {
+		reg = <0x300 0x100>;
+		interrupt-controller;
+		#interrupt-cells = <2>;
+		interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>;
+	};
+};