add a DT binding documentation of usb3.0 phy for MT65xx
SoCs from Mediatek.

Signed-off-by: Chunfeng Yun <chunfeng.yun-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
---
 .../devicetree/bindings/usb/mt65xx-u3phy.txt       | 34 ++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/usb/mt65xx-u3phy.txt

diff --git a/Documentation/devicetree/bindings/usb/mt65xx-u3phy.txt b/Documentation/devicetree/bindings/usb/mt65xx-u3phy.txt
new file mode 100644
index 0000000..056b2aa
--- /dev/null
+++ b/Documentation/devicetree/bindings/usb/mt65xx-u3phy.txt

@@ -0,0 +1,34 @@
+MT65xx U3PHY
+
+The device node for Mediatek SOC usb3.0 phy
+
+Required properties:
+ - compatible : Should be "mediatek,mt8173-u3phy"
+ - reg        : Offset and length of registers, the first is for mac domain,
+	another for phy domain
+ - power-domains: to enable usb's mtcmos
+ - usb-wakeup-ctrl : to access usb wakeup control register
+ - wakeup-src : 1: ip sleep wakeup mode; 2: line state wakeup mode; others
+	means don't enable wakeup source of usb
+ - u2port-num : number of usb2.0 ports to support which should be 1 or 2
+ - clocks     : must support all clocks that phy need
+ - clock-names: should be "wakeup_deb_p0", "wakeup_deb_p1" for wakeup
+	debounce control clocks, and "u3phya_ref" for u3phya reference clock.
+
+Example:
+
+u3phy: usb-phy@11271000 {
+	compatible = "mediatek,mt8173-u3phy";
+	reg = <0 0x11271000 0 0x3000>,
+	      <0 0x11280000 0 0x20000>;