CONFIG_ARCH_BCM_5301X is not available for the default architecture x86.
Result is shown for architecture arm

Broadcom BCM470X / BCM5301X ARM SoC

modulename: bcm_5301x.ko
configname: CONFIG_ARCH_BCM_5301X

Linux Kernel Configuration
└─> Broadcom SoC Support
└─> Broadcom BCM470X / BCM5301X ARM SoC

Support for Broadcom BCM470X and BCM5301X SoCs with ARM CPU cores.

This is a network SoC line mostly used in home routers and
wifi access points, its internal name is Northstar.
This includes the following SoC: BCM53010, BCM53011, BCM53012,
BCM53014, BCM53015, BCM53016, BCM53017, BCM53018, BCM4707,
BCM4708 and BCM4709.

Do not confuse this with the BCM4760 which is a totally
different SoC or with the older BCM47XX and BCM53XX based
network SoC using a MIPS CPU, they are supported by arch/mips/bcm47xx

source code: