Documentation: dts: Update section header for APM X-Gene

Signed-off-by: NIyappan Subramanian <isubramanian@apm.com>
Signed-off-by: NKeyur Chudgar <kchudgar@apm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/apm-xgene-enet.txt

@@ -3,7 +3,7 @@ APM X-Gene SoC Ethernet nodes
 Ethernet nodes are defined to describe on-chip ethernet interfaces in
 APM X-Gene SoC.
 
-Required properties:
+Required properties for all the ethernet interfaces:
 - compatible: Should be "apm,xgene-enet"
 - reg: Address and length of the register set for the device. It contains the
   information of registers in the same order as described by reg-names
@@ -15,6 +15,8 @@ Required properties:
 - clocks: Reference to the clock entry.
 - local-mac-address: MAC address assigned to this device
 - phy-connection-type: Interface type between ethernet device and PHY device
+
+Required properties for ethernet interfaces that have external PHY:
 - phy-handle: Reference to a PHY node connected to this device
 
 - mdio: Device tree subnode with the following required properties: