dt-bindings: interrupt-controller: loongson ls1x intc

Dt-bindings doc about Loongson-1 interrupt controller.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/devicetree/bindings/interrupt-controller/loongson,ls1x-intc.txt

+Loongson ls1x Interrupt Controller
+
+Required properties:
+
+- compatible : should be "loongson,ls1x-intc". Valid strings are:
+
+- 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 2.
+- interrupts : Specifies the CPU interrupt the controller is connected to.
+
+Example:
+
+intc: interrupt-controller@1fd01040 {
+	compatible = "loongson,ls1x-intc";
+	reg = <0x1fd01040 0x18>;
+
+	interrupt-controller;
+	#interrupt-cells = <2>;
+
+	interrupt-parent = <&cpu_intc>;
+	interrupts = <2>;
+};