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

FootBridge

configname: CONFIG_ARCH_FOOTBRIDGE

ARM system type
└─>FootBridge
In linux kernel since version 2.6.12  
Support for systems based on the DC21285 companion chip
("FootBridge"), such as the Simtec CATS and the Rebel NetWinder.


depends
 or CONFIG_ARCH_MULTI_V4 |
| CONFIG_ATAGS or CONFIG_CPU_LITTLE_ENDIAN or CONFIG_MMU or  NOT CONFIG_ARCH_GEMINI or  NOT CONFIG_ARCH_MOXART or  NOT CONFIG_ARCH_MULTI_V4T or  NOT CONFIG_ARCH_MULTI_V5 or  NOT CONFIG_ARCH_SA1100