This is currently implemented in net/eth.c
Look in include/net.h for details.
+config PHYLIB
+ bool "Ethernet PHY (physical media interface) support"
+ help
+ Enable Ethernet PHY (physical media interface) support.
+
menuconfig NETDEVICES
bool "Network device support"
depends on NET
100Mbit and 1 Gbit operation. You must enable CONFIG_PHYLIB to
provide the PHY (physical media interface).
+config PCH_GBE
+ bool "Intel Platform Controller Hub EG20T GMAC driver"
+ depends on DM_ETH && DM_PCI
+ select PHYLIB
+ help
+ This MAC is present in Intel Platform Controller Hub EG20T. It
+ supports 10/100/1000 Mbps operation.
+
endif # NETDEVICES