CONFIG_DEBUG_S3C_UART3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Use Samsung S3C UART 3 for low-level debug

configname: CONFIG_DEBUG_S3C_UART3

Kernel low-level debugging port
└─>Use Samsung S3C UART 3 for low-level debug
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Say Y here if you want the debug print routines to direct
their output to UART 3. The port must have been initialised
by the boot-loader before use.