default or selected kernelversion does not have config value CONFIG_AR600x_CUSTOM_XXX.
Result is shown for kernelversion 6.2.5

CUSTOM-xxx

configname: CONFIG_AR600x_CUSTOM_XXX

AR6003 Board Data Configuration
└─>CUSTOM-xxx
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Board Data file for a custom reference design (File: should be named as bdata.CUSTOM.bin)