CONFIG_DEBUG_SIRFSOC_UART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_DEBUG_SIRFSOC_UART (not configurable)

configname: CONFIG_DEBUG_SIRFSOC_UART

Linux Kernel Configuration
└─>Kernel hacking
└─>DEBUG_SIRFSOC_UART
In linux kernel since version 4 (release Date: 2015-04-12)