Optional properties:
- clocks : phandle + phy specifier pair, for the input clock of phy.
- clock-names : input clock name of phy, must be "phyclk".
+ - rockchip,u2phy-tuning; when set, tuning u2phy to improve usb2 SI.
Required nodes : a sub-node is required for each port the phy provides.
The sub-node name is used to identify host or otg port,