devicetree: document Ingenic SoC interrupt controller binding

Add binding documentation for Ingenic SoC interrupt controllers.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: devicetree@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10134/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Documentation/devicetree/bindings/interrupt-controller/ingenic,intc.txt

+Ingenic SoC Interrupt Controller
+
+Required properties:
+
+- compatible : should be "ingenic,<socname>-intc". Valid strings are:
+    ingenic,jz4740-intc
+    ingenic,jz4770-intc
+    ingenic,jz4775-intc
+    ingenic,jz4780-intc
+- reg : Specifies base physical address and size of the registers.
+- interrupt-controller : Identifies the node as an interrupt controller
+- #interrupt-cells : Specifies the number of cells needed to encode an
+  interrupt source. The value shall be 1.
+- interrupt-parent : phandle of the CPU interrupt controller.
+- interrupts : Specifies the CPU interrupt the controller is connected to.
+
+Example:
+
+intc: interrupt-controller@10001000 {
+	compatible = "ingenic,jz4740-intc";
+	reg = <0x10001000 0x14>;
+
+	interrupt-controller;
+	#interrupt-cells = <1>;
+
+	interrupt-parent = <&cpuintc>;
+	interrupts = <2>;
+};