diff --git a/Documentation/devicetree/bindings/net/xilinx_axienet.txt b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
index 0be335c7abede290a74967276f592a4471311acd..a8be67b425fd7db3185e5f9ac3efc1151ac956c8 100644
--- a/Documentation/devicetree/bindings/net/xilinx_axienet.txt
+++ b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
@@ -37,6 +37,9 @@ Optional properties:
 		  auto-detected from the CPU clock (but only on platforms where
 		  this is possible). New device trees should specify this - the
 		  auto detection is only for backward compatibility.
+ - mdio		: Child node for MDIO bus. Must be defined if PHY access is
+		  required through the core's MDIO interface (i.e. always,
+		  unless the PHY is accessed through a different bus).
 
 Example:
 	axi_ethernet_eth: ethernet@40c00000 {