CONFIG_DEBUG_BCM2835 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging on BCM2835 PL011 UART

configname: CONFIG_DEBUG_BCM2835

Kernel low-level debugging port
└─>Kernel low-level debugging on BCM2835 PL011 UART
In linux kernel since version 3.1 (release Date: 2011-10-24)