CONFIG_RTLBTCOEXIST (not configurable)

modulename: btcoexist.ko

configname: CONFIG_RTLBTCOEXIST

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Wireless LAN
└─>Realtek rtlwifi family of devices
└─>RTLBTCOEXIST
In linux kernel since version 3.15 (release Date: 2014-06-08)  
source code:
drivers/net/wireless/realtek/rtlwifi/btcoexist/