CONFIG_OF_MDIO (not configurable)

modulename: of_mdio.ko

configname: CONFIG_OF_MDIO

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>MDIO bus device drivers
└─>Device Tree and Open Firmware support
└─>PHY Device support and infrastructure
└─>OF_MDIO
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
OpenFirmware MDIO bus (Ethernet PHY) accessors

source code: