CONFIG_PPC_UDBG_BEAT is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

BEAT based debug console

modulename: beat_udbg.ko

configname: CONFIG_PPC_UDBG_BEAT

Linux Kernel Configuration
└─>Platform support
└─>BEAT based debug console
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
source code:
arch/powerpc/platforms/cell/beat_udbg.c