Qualcomm Technologies, Inc. MSM PHY Transceivers

Required properties:
- compatible: Should be "qcom,usb-ssphy"
- reg: Address and length of the register set for the device
- clocks: a list of handles to the PHY clocks. Use as per
  Documentation/devicetree/bindings/clock/clock-bindings.txt
- clock-names: Names of the clocks in 1-1 correspondence with the "clocks"
  property. "ref_clk", "cfg_ahb_clk" and "pipe_clk" are mandatory.
- <supply-name>-supply: phandle to the regulator device tree node
Required "supply-name" examples are:
"vdd" : vdd supply for SSPHY digital circuit operation
"vdda18" : 1.8v high-voltage analog supply for SSPHY
- qcom,vdd-voltage-level: This property must be a list of three integer
values (no, min, max) where each value represents either a voltage in
microvolts or a value corresponding to voltage corner

Optional properties:
- qcom,vbus-valid-override: If present, indicates VBUS pin is not connected to
the USB PHY and the controller must rely on external VBUS notification in
order to manually relay the notification to the SSPHY.
-qcom,keep-powerdown: If present, power down the SSPHY to avoid leakage current.

Example:
ssphy@f9200000 {
	compatible = "qcom,usb-ssphy";
	reg = <0xf9200000 0xfc000>;
	vdd-supply = <&pm8841_s2_corner>;
	vdda18-supply = <&pm8941_l6>;
	qcom,vdd-voltage-level = <1 5 7>;
	clocks = <&clock_gcc USB_PHY_REF_CLK>,
		 <&clock_gcc USB_PHY_CFG_AHB_CLK>,
		 <&clock_gcc USB_PHY_PIPE_CLK>;
	clock-names = "ref_clk", "cfg_ahb_clk", "pipe_clk";
};