CONFIG_ETRAX_CMDLINE is not available for thedefaultarchitecture x86.
Result is shown for architecture cris
default or selected kernelversion does not have config value CONFIG_ETRAX_CMDLINE.
Result is shown for kernelversion 6.7-rc3

Kernel command line

configname: CONFIG_ETRAX_CMDLINE

Linux Kernel Configuration
└─>General setup
└─>Kernel command line
In linux kernel since version 2.6.12  
Pass additional commands to the kernel.