dt-bindings: interrupt-controller: C-SKY APB intc

 - Dt-bindings doc about C-SKY apb bus interrupt controller.
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/interrupt-controller/csky,apb-intc.txt

+==============================
+C-SKY APB Interrupt Controller
+==============================
+
+C-SKY APB Interrupt Controller is a simple soc interrupt controller
+on the apb bus and we only use it as root irq controller.
+
+ - csky,apb-intc is used in a lot of csky fpgas and socs, it support 64 irq nums.
+ - csky,dual-apb-intc consists of 2 apb-intc and 128 irq nums supported.
+ - csky,gx6605s-intc is gx6605s soc internal irq interrupt controller, 64 irq nums.
+
+=============================
+intc node bindings definition
+=============================
+
+	Description: Describes APB interrupt controller
+
+	PROPERTIES
+
+	- compatible
+		Usage: required
+		Value type: <string>
+		Definition: must be "csky,apb-intc"
+				    "csky,dual-apb-intc"
+				    "csky,gx6605s-intc"
+	- #interrupt-cells
+		Usage: required
+		Value type: <u32>
+		Definition: must be <1>
+	- reg
+		Usage: required
+		Value type: <u32 u32>
+		Definition: <phyaddr size> in soc from cpu view
+	- interrupt-controller:
+		Usage: required
+	- csky,support-pulse-signal:
+		Usage: select
+		Description: to support pulse signal flag
+
+Examples:
+---------
+
+	intc: interrupt-controller@500000 {
+		compatible = "csky,apb-intc";
+		#interrupt-cells = <1>;
+		reg = <0x00500000 0x400>;
+		interrupt-controller;
+	};
+
+	intc: interrupt-controller@500000 {
+		compatible = "csky,dual-apb-intc";
+		#interrupt-cells = <1>;
+		reg = <0x00500000 0x400>;
+		interrupt-controller;
+	};
+
+	intc: interrupt-controller@500000 {
+		compatible = "csky,gx6605s-intc";
+		#interrupt-cells = <1>;
+		reg = <0x00500000 0x400>;
+		interrupt-controller;
+	};