CONFIG_DEBUG_BCM2836 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging on BCM2836 PL011 UART

configname: CONFIG_DEBUG_BCM2836

Kernel low-level debugging port
└─>Kernel low-level debugging on BCM2836 PL011 UART
In linux kernel since version 4.1 (release Date: 2015-06-21)