diff --git a/Documentation/devicetree/bindings/usb/usb-device.txt b/Documentation/devicetree/bindings/usb/usb-device.txt
index e0b562e35a0c69b667206bb262d2e84b6c02d8f3..1b27cebb47f4286f8fac429f1361e6cba240d469 100644
--- a/Documentation/devicetree/bindings/usb/usb-device.txt
+++ b/Documentation/devicetree/bindings/usb/usb-device.txt
@@ -4,22 +4,34 @@ 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 port number which this device is connecting to, the range
-  is 1-255.
+- 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 {
+&usb1 {	/* host controller */
 	#address-cells = <1>;
 	#size-cells = <0>;
 
-	hub@1 {
+	hub@1 {	/* hub connected to port 1 */
 		compatible = "usb5e3,608";
 		reg = <1>;
 	};