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

ETRAX FS serial console support

configname: CONFIG_SERIAL_ETRAXFS_CONSOLE

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>Serial drivers
└─>ETRAX FS serial console support
In linux kernel since version 4 (release Date: 2015-04-12)