DT: net: document Ethernet bindings in one place

This patch is an attempt to gather the Ethernet related bindings in one file,
like it's done in the MMC and some other subsystems. It should save some of
the trouble of documenting several properties over and over in each binding
document, instead only making reference to the main file.

I have used the Embedded Power Architecture(TM) Platform Requirements (ePAPR)
standard as a base for the properties description, also documenting some ad-hoc
properties that have been introduced over time despite having direct analogs in
ePAPR.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Documentation/devicetree/bindings/net/fsl-fec.txt b/Documentation/devicetree/bindings/net/fsl-fec.txt
index 845ff84..6bc84ad 100644
--- a/Documentation/devicetree/bindings/net/fsl-fec.txt
+++ b/Documentation/devicetree/bindings/net/fsl-fec.txt
@@ -4,12 +4,9 @@
 - compatible : Should be "fsl,<soc>-fec"
 - reg : Address and length of the register set for the device
 - interrupts : Should contain fec interrupt
-- phy-mode : String, operation mode of the PHY interface.
-  Supported values are: "mii", "gmii", "sgmii", "tbi", "rmii",
-  "rgmii", "rgmii-id", "rgmii-rxid", "rgmii-txid", "rtbi", "smii".
+- phy-mode : See ethernet.txt file in the same directory
 
 Optional properties:
-- local-mac-address : 6 bytes, mac address
 - phy-reset-gpios : Should specify the gpio for phy reset
 - phy-reset-duration : Reset duration in milliseconds.  Should present
   only if property "phy-reset-gpios" is available.  Missing the property