dt-bindings: net: ftgmac100: Describe clock properties

Critically, the AST2600 requires ungating the RMII RCLK if e.g. NCSI is
in use.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Acked-by: Joel Stanley <joel@jms.id.au>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/ftgmac100.txt

@@ -24,6 +24,13 @@ Optional properties:
 - no-hw-checksum: Used to disable HW checksum support. Here for backward
   compatibility as the driver now should have correct defaults based on
   the SoC.
+- clocks: In accordance with the generic clock bindings. Must describe the MAC
+  IP clock, and optionally an RMII RCLK gate for the AST2500/AST2600. The
+  required MAC clock must be the first cell.
+- clock-names:
+
+      - "MACCLK": The MAC IP clock
+      - "RCLK": Clock gate for the RMII RCLK
 
 Example: