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

It adds device tree bindings document for HiSilicon INNO USB2 PHY.
Signed-off-by: NPengcheng Li <lpc.li@hisilicon.com>
Signed-off-by: NJiancheng Xue <xuejiancheng@hisilicon.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NKishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/phy/phy-hisi-inno-usb2.txt

+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>;
+		};
+	};
+};