CONFIG_BF53x is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin

CONFIG_BF53x (not configurable)

configname: CONFIG_BF53x

Linux Kernel Configuration
└─>Blackfin Processor Options
└─>BF53x
In linux kernel since version 2.6.24 (release Date: 2008-01-24)