dt-bindings: usb: rt1711h device tree binding document

Add device tree binding document for Richtek RT1711H Type-C chip driver
Signed-off-by: NShuFan Lee <shufan_lee@richtek.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/richtek,rt1711h.txt

+Richtek RT1711H TypeC PD Controller.
+
+Required properties:
+ - compatible : Must be "richtek,rt1711h".
+ - reg : Must be 0x4e, it's slave address of RT1711H.
+ - interrupt-parent : the phandle for the interrupt controller that
+   provides interrupts for this device.
+ - interrupts : <a b> where a is the interrupt number and b represents an
+   encoding of the sense and level information for the interrupt.
+
+Example :
+rt1711h@4e {
+	compatible = "richtek,rt1711h";
+	reg = <0x4e>;
+	interrupt-parent = <&gpio26>;
+	interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
+};