CONFIG_FEC_ENET is not available for thedefaultarchitecture x86.
Result is shown for architecture ppc
default or selected kernelversion does not have config value CONFIG_FEC_ENET.
Result is shown for kernelversion 5.4.123

FCC Ethernet

modulename: fcc_enet.ko

and/or

fec.ko

configname: CONFIG_FEC_ENET

Linux Kernel Configuration
└─>CPM2 Options
└─>FCC Ethernet
In linux kernel since version 2.6.12  
source code:
arch/ppc/8260_io/fcc_enet.c
depends
CONFIG_CPM2
CONFIG_NET_ETHERNET or CONFIG_8xx