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

CONFIG_ARCH_BCM_MOBILE (not configurable)

configname: CONFIG_ARCH_BCM_MOBILE

Linux Kernel Configuration
└─>Broadcom SoC Support
└─>ARCH_BCM_MOBILE
In linux kernel since version 3.10 (release Date: 2013-06-30)  
This enables support for systems based on Broadcom mobile SoCs.