CONFIG_DEBUG_FOOTBRIDGE_COM1 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Kernel low-level debugging messages via footbridge 8250 at PCI COM1

configname: CONFIG_DEBUG_FOOTBRIDGE_COM1

Kernel low-level debugging port
└─>Kernel low-level debugging messages via footbridge 8250 at PCI COM1
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 the 8250 at PCI COM1.