CONFIG_DEBUG_BCM63XX_UART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging on BCM63XX UART

configname: CONFIG_DEBUG_BCM63XX_UART

Kernel low-level debugging port
└─>Kernel low-level debugging on BCM63XX UART
In linux kernel since version 3.10 (release Date: 2013-06-30)