Generic USB Device Properties

Usually, we only use device tree for hard wired USB device.
The reference binding doc is from:
http://www.devicetree.org/open-firmware/bindings/usb/usb-1_0.ps


Required properties:
- compatible: "usbVID,PID", where VID is the vendor id and PID the product id.
  The textual representation of VID and PID shall be in lower case hexadecimal
  with leading zeroes suppressed. The other compatible strings from the above
  standard binding could also be used, but a device adhering to this binding
  may leave out all except for "usbVID,PID".
- reg: the number of the USB hub port or the USB host-controller port to which
  this device is attached. The range is 1-255.


Required properties for hub nodes with device nodes:
- #address-cells: shall be 1
- #size-cells: shall be 0


Required properties for host-controller nodes with device nodes:
- #address-cells: shall be 1
- #size-cells: shall be 0


Example:

&usb1 {	/* host controller */
	#address-cells = <1>;
	#size-cells = <0>;

	hub@1 {	/* hub connected to port 1 */
		compatible = "usb5e3,608";
		reg = <1>;
	};
};