CONFIG_DEBUG_TI81XXUART3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

TI81XX UART3 (ti8168evm)

configname: CONFIG_DEBUG_TI81XXUART3

Low-level debug console UART
└─>TI81XX UART3 (ti8168evm)
In linux kernel since version 3.1 (release Date: 2011-10-24)  

depends
 or CONFIG_ARCH_OMAP2PLUS