CONFIG_ARCH_NS9XXX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_NS9XXX.
Result is shown for kernelversion 5.4.69

NetSilicon NS9xxx

configname: CONFIG_ARCH_NS9XXX

ARM system type
└─>NetSilicon NS9xxx
In linux kernel since version 2.6.21 (release Date: 2007-04-25)  
Say Y here if you intend to run this kernel on a NetSilicon NS9xxx