If you say Y here, it will be possible to remotely debug the
kernel using gdb. It is recommended but not required, that
you also turn on the kernel config option
CONFIG_FRAME_POINTER to aid in producing more reliable stack
backtraces in the external debugger. Documentation of
kernel debugger is available at http://kgdb.sourceforge.net
as well as in DocBook form in Documentation/DocBook/. If
unsure, say N.

source code:

arch/mn10300/kernel/kgdb.c