CONFIG_DEBUG_IMX50_IMX53_UART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_DEBUG_IMX50_IMX53_UART.
Result is shown for kernelversion 5.3.7

i.MX50 and i.MX53 Debug UART


Kernel low-level debugging port
└─>i.MX50 and i.MX53 Debug UART
In linux kernel since version 3.3 (release Date: 2012-03-18)  
Say Y here if you want kernel low-level debugging support
on i.MX50 or i.MX53.