dt-bindings: add bindings doc for HiSilicon INNO USB2 PHY

Device tree bindings for HiSilicon INNO USB2 PHY

Required properties:

- compatible: Should be one of the following strings:

	"hisilicon,inno-usb2-phy",

	"hisilicon,hi3798cv200-usb2-phy".

- reg: Should be the address space for PHY configuration register in peripheral

  controller, e.g. PERI_USB0 for USB 2.0 PHY01 on Hi3798CV200 SoC.

- clocks: The phandle and clock specifier pair for INNO USB2 PHY device

  reference clock.

- resets: The phandle and reset specifier pair for INNO USB2 PHY device reset

  signal.

- #address-cells: Must be 1.

- #size-cells: Must be 0.

The INNO USB2 PHY device should be a child node of peripheral controller that

contains the PHY configuration register, and each device suppports up to 2 PHY

ports which are represented as child nodes of INNO USB2 PHY device.

Required properties for PHY port node:

- reg: The PHY port instance number.

- #phy-cells: Defined by generic PHY bindings.  Must be 0.

- resets: The phandle and reset specifier pair for PHY port reset signal.

Refer to phy/phy-bindings.txt for the generic PHY binding properties

Example:

perictrl: peripheral-controller@8a20000 {

	compatible = "hisilicon,hi3798cv200-perictrl", "simple-mfd";

	reg = <0x8a20000 0x1000>;

	#address-cells = <1>;

	#size-cells = <1>;

	ranges = <0x0 0x8a20000 0x1000>;

	usb2_phy1: usb2-phy@120 {

		compatible = "hisilicon,hi3798cv200-usb2-phy";

		reg = <0x120 0x4>;

		clocks = <&crg HISTB_USB2_PHY1_REF_CLK>;

		resets = <&crg 0xbc 4>;

		#address-cells = <1>;

		#size-cells = <0>;

		usb2_phy1_port0: phy@0 {

			reg = <0>;

			#phy-cells = <0>;

			resets = <&crg 0xbc 8>;

		};

		usb2_phy1_port1: phy@1 {

			reg = <1>;

			#phy-cells = <0>;

			resets = <&crg 0xbc 9>;

		};

	};

	usb2_phy2: usb2-phy@124 {

		compatible = "hisilicon,hi3798cv200-usb2-phy";

		reg = <0x124 0x4>;

		clocks = <&crg HISTB_USB2_PHY2_REF_CLK>;

		resets = <&crg 0xbc 6>;

		#address-cells = <1>;

		#size-cells = <0>;

		usb2_phy2_port0: phy@0 {

			reg = <0>;

			#phy-cells = <0>;

			resets = <&crg 0xbc 10>;

		};

	};

};