CONFIG_BT_RTL (not configurable)

modulename: btrtl.ko

configname: CONFIG_BT_RTL

Linux Kernel Configuration
└─>Networking support
└─>Bluetooth subsystem support
└─>Bluetooth device drivers
└─>BT_RTL
In linux kernel since version 4.1 (release Date: 2015-06-21)  
source code:
drivers/bluetooth/btrtl.c