CONFIG_MIPS_CPS_NS16550_BASE is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

UART Base Address

configname: CONFIG_MIPS_CPS_NS16550_BASE

Linux Kernel Configuration
└─>CPS SMP NS16550 UART output
└─>UART Base Address
In linux kernel since version 4.1 (release Date: 2015-06-21)  
The base address of the ns16550 compatible UART on which to output
debug information from the early stages of core startup.

This is only used if non-zero.