usb: dwc3: rockchip-inno: add devicetree bindings documentation

This patch adds the devicetree documentation required for Rockchip
USB 3.0 core wrapper consisting of USB 3.0 controller IP from Synopsys
and USB 3.0 PHY IP from Innosilicon.

It supports DRD mode, and could operate in device mode (SS, HS, FS)
and host mode (SS, HS, FS, LS).

Change-Id: Ia240627c31cd3ff2f2d7f1a1faa9c7d88207d04f
Signed-off-by: William Wu <wulf@rock-chips.com>

Documentation/devicetree/bindings/usb/rockchip-inno,dwc3.txt

@@ -0,0 +1,59 @@
+Rockchip SuperSpeed DWC3 USB SoC controller with INNO USB3 PHY inside
+
+Required properties:
+- compatible : should be one of the listed compatibles:
+  * "rockchip,rk3328-dwc3"
+  * "rockchip,rk322xh-dwc3"
+- clocks : a list of phandle + clock-specifier pairs for the
+	   clocks listed in clock-names.
+- clock-names : Should contain the following:
+  * "ref_clk" for controller reference clk, have to be 24 MHz
+  * "suspend_clk" for controller suspend clk, have to be 24 MHz or 32 KHz
+  * "bus_clk" for master/Core clock, have to be >= 62.5 MHz for SS
+	      operation and >= 30MHz for HS operation.
+
+Required child node:
+A child node must exist to represent the core DWC3 IP block. The name of
+the node is not important. The content of the node is defined in dwc3.txt.
+
+Phy documentation is provided in the following places:
+Documentation/devicetree/bindings/phy/phy-rockchip-inno-usb3.txt
+
+Example device nodes:
+
+	u3phy: usb3-phy@ff470000 {
+		compatible = "rockchip,rk3328-u3phy";
+		reg = <0x0 0xff470000 0x0 0x0>;
+		...
+
+		u3phy_utmi: utmi@ff470000 {
+			reg = <0x0 0xff470000 0x0 0x8000>;
+			#phy-cells = <0>;
+		};
+
+		u3phy_pipe: pipe@ff478000 {
+			reg = <0x0 0xff478000 0x0 0x8000>;
+			#phy-cells = <0>;
+		};
+	};
+
+	usbdrd3: usb@ff600000 {
+		compatible = "rockchip,rk3328-dwc3";
+		clocks = <&cru SCLK_USB3OTG_REF>, <&cru SCLK_USB3OTG_SUSPEND>,
+			 <&cru ACLK_USB3OTG>;
+		clock-names = "ref_clk", "suspend_clk",
+			      "bus_clk";
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		usbdrd_dwc3: dwc3@ff600000 {
+			compatible = "snps,dwc3";
+			reg = <0x0 0xff600000 0x0 0x100000>;
+			interrupts = <GIC_SPI 67 IRQ_TYPE_LEVEL_HIGH>;
+			dr_mode = "host";
+			phys = <&u3phy_utmi>, <&u3phy_pipe>;
+			phy-names = "usb2-phy", "usb3-phy";
+			phy_type = "utmi_wide";
+		};
+	};