CONFIG_4xx_SOC is not available for the selected architecture x86.
Result is shown for architecture powerpc

CONFIG_4xx_SOC (not configurable)

modulename: soc.ko

configname: CONFIG_4xx_SOC

Linux Kernel Configuration
└─>Bus options
└─>4xx_SOC
In linux kernel since version 2.6.26 (release Date: 2008-07-13)
source code:
arch/powerpc/platforms/4xx/soc.c