default or selected kernelversion does not have config value CONFIG_NET_SB1250_MAC.
Result is shown for kernelversion 5.4.123

SB1250 Ethernet support

modulename: sb1250-mac.ko

configname: CONFIG_NET_SB1250_MAC

Linux Kernel Configuration
└─>Networking support
└─>Ethernet (10 or 100Mbit)
└─>SB1250 Ethernet support
In linux kernel since version 2.6.12  
source code:
drivers/net//sb1250-mac.c