CONFIG_DEBUG_BCM63XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging on BCM63XX UART

configname: CONFIG_DEBUG_BCM63XX

Kernel low-level debugging port
└─>Kernel low-level debugging on BCM63XX UART
In linux kernel since version 3.18 (release Date: 2014-12-07)