irqchip: Devicetree: document Conexant Digicolor irq binding

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/505a65c8861e5210d94227bc0eec89cab0593fca.1421317616.git.baruch@tkos.co.ilSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Documentation/devicetree/bindings/interrupt-controller/digicolor-ic.txt

+Conexant Digicolor Interrupt Controller
+
+Required properties:
+
+- compatible : should be "cnxt,cx92755-ic"
+- reg : Specifies base physical address and size of the interrupt controller
+  registers (IC) area
+- 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.
+- syscon: A phandle to the syscon node describing UC registers
+
+Example:
+
+	intc: interrupt-controller@f0000040 {
+		compatible = "cnxt,cx92755-ic";
+		interrupt-controller;
+		#interrupt-cells = <1>;
+		reg = <0xf0000040 0x40>;
+		syscon = <&uc_regs>;
+	};