default or selected kernelversion does not have config value CONFIG_SERIAL_ETRAXFS.
Result is shown for kernelversion 6.7-rc3

ETRAX FS serial port support

modulename: etraxfs-uart.ko

configname: CONFIG_SERIAL_ETRAXFS

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>Device Tree and Open Firmware support
└─>ETRAX FS serial port support
In linux kernel since version 4 (release Date: 2015-04-12)  
source code: