diff --git a/include/net/if.h b/include/net/if.h
index 7afcc2d15a..2e869d6b24 100644
--- a/include/net/if.h
+++ b/include/net/if.h
@@ -127,6 +127,17 @@
 #  define IFF_IS_IPv4(f)   (1)
 #endif
 
+/* MDIO Manageable Device (MMD) support with SIOCxMIIREG ioctl commands */
+
+#define MDIO_PHY_ID_C45      0x8000
+#define MDIO_PHY_ID_PRTAD    0x03E0
+#define MDIO_PHY_ID_DEVAD    0x001F
+#define MDIO_PHY_ID_C45_MASK \
+    (MDIO_PHY_ID_C45 | MDIO_PHY_ID_PRTAD | MDIO_PHY_ID_DEVAD)
+
+#define mdio_phy_id_c45(prtad, devad) \
+    ((uint16_t)(MDIO_PHY_ID_C45 | ((prtad) << 5) | (devad)))
+
 /* RFC 2863 operational status */
 
 enum
diff --git a/include/nuttx/net/netdev.h b/include/nuttx/net/netdev.h
index c31ce180d7..460420b74c 100644
--- a/include/nuttx/net/netdev.h
+++ b/include/nuttx/net/netdev.h
@@ -2,7 +2,8 @@
  * include/nuttx/net/netdev.h
  *
  * SPDX-License-Identifier: BSD-3-Clause
- * SPDX-FileCopyrightText: 2007, 2009, 2011-2018 Gregory Nutt. All rights reserved.
+ * SPDX-FileCopyrightText: 2007,2009 Gregory Nutt. All rights reserved.
+ * SPDX-FileCopyrightText: 2011-2018 Gregory Nutt. All rights reserved.
  * SPDX-FileCopyrightText: 2001-2003, Adam Dunkels. All rights reserved.
  * SPDX-FileContributor: Gregory Nutt <gnutt@nuttx.org>
  *
@@ -216,6 +217,17 @@
      (netdev_ipv6_lookup(dev, addr, true) != NULL)
 #endif
 
+/* MDIO Manageable Device (MMD) support with SIOCxMIIREG ioctl commands */
+
+#define mdio_phy_id_is_c45(phy_id) \
+    (((phy_id) & MDIO_PHY_ID_C45) && !((phy_id) & ~MDIO_PHY_ID_C45_MASK))
+
+#define mdio_phy_id_prtad(phy_id) \
+    ((uint16_t)(((phy_id) & MDIO_PHY_ID_PRTAD) >> 5))
+
+#define mdio_phy_id_devad(phy_id) \
+    ((uint16_t)((phy_id) & MDIO_PHY_ID_DEVAD))
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/