CONFIG_ARCH_BCM2835 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Broadcom BCM2835 family

modulename: irq-bcm2835.ko

and/or

bcm2835_timer.ko

and/or

clk-bcm2835.ko

configname: CONFIG_ARCH_BCM2835

Linux Kernel Configuration
└─>Broadcom BCM2835 family
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This enables support for the Broadcom BCM2835 SoC. This SoC is
used in the Raspberry Pi and Roku 2 devices.

source code:
drivers/irqchip/irq-bcm2835.c