CONFIG_NS9XXX_HAVE_SERIAL8250 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_NS9XXX_HAVE_SERIAL8250.
Result is shown for kernelversion 5.4.69

CONFIG_NS9XXX_HAVE_SERIAL8250 (not configurable)

modulename: plat-serial8250.ko

configname: CONFIG_NS9XXX_HAVE_SERIAL8250

Linux Kernel Configuration
└─>NS9xxx Implementations
└─>NS9XXX_HAVE_SERIAL8250
In linux kernel since version 2.6.26 (release Date: 2008-07-13)  
source code: