Required properties:
- compatible: "renesas,usb-phy-r8a7790" if the device is a part of R8A7790 SoC.
"renesas,usb-phy-r8a7791" if the device is a part of R8A7791 SoC.
+ "renesas,usb-phy-r8a7794" if the device is a part of R8A7794 SoC.
- reg: offset and length of the register block.
- #address-cells: number of address cells for the USB channel subnodes, must
be <1>.