default or selected kernelversion does not have config value CONFIG_OF_NET.
Result is shown for kernelversion 6.9.9

CONFIG_OF_NET (not configurable)

modulename: of_net.ko

configname: CONFIG_OF_NET

Linux Kernel Configuration
└─>Device Drivers
└─>Device Tree and Open Firmware support
└─>OF_NET
In linux kernel since version 2.6.38 (release Date: 2011-03-14)  
source code:
drivers/of/of_net.c

is selected by
CONFIG_AMD_XGBE