CONFIG_REGMAP (not configurable)

modulename: regmap.ko

and/or

regcache-rbtree.ko

configname: CONFIG_REGMAP

Linux Kernel Configuration
└─>Device Drivers
└─>Generic Driver Options
└─>REGMAP
In linux kernel since version 3.1 (release Date: 2011-10-24)  
Enable support for the Register Map (regmap) access API.

Usually, this option is automatically selected when needed.
However, you may want to enable it manually for running the regmap
KUnit tests.

If unsure, say N.

source code:
drivers/base//regmap/
selects
CONFIG_IRQ_DOMAIN
CONFIG_MDIO_BUS