CONFIG_DEBUG_MSM_UART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_DEBUG_MSM_UART.
Result is shown for kernelversion 6.5.1

CONFIG_DEBUG_MSM_UART (not configurable)

configname: CONFIG_DEBUG_MSM_UART

Linux Kernel Configuration
└─>Kernel hacking
└─>DEBUG_MSM_UART
In linux kernel since version 3.13 (release Date: 2014-01-19)  
depends
CONFIG_ARCH_MSM