CONFIG_CPU_N15 is not available for thedefaultarchitecture x86.
Result is shown for architecture nds32
default or selected kernelversion does not have config value CONFIG_CPU_N15.
Result is shown for kernelversion 6.9.9

AndesCore N15

configname: CONFIG_CPU_N15

minimum CPU type
└─>AndesCore N15
In linux kernel since version 4.2 (release Date: 2015-08-30)