Bluetooth is low-cost, low-power, short-range wireless technology.
It was designed as a replacement for cables and other short-range
technologies like IrDA. Bluetooth operates in personal area range
that typically extends up to 10 meters. More information about
Bluetooth can be found at <https://www.bluetooth.com/>.

Linux Bluetooth subsystem consist of several layers:
Bluetooth Core
HCI device and connection manager, scheduler
SCO audio links
L2CAP (Logical Link Control and Adaptation Protocol)
SMP (Security Manager Protocol) on LE (Low Energy) links
HCI Device drivers (Interface to the hardware)
RFCOMM Module (RFCOMM Protocol)
BNEP Module (Bluetooth Network Encapsulation Protocol)
CMTP Module (CAPI Message Transport Protocol)
HIDP Module (Human Interface Device Protocol)

Say Y here to compile Bluetooth support into the kernel or say M to
compile it as module (bluetooth).

To use Linux Bluetooth subsystem, you will need several user-space
utilities like hciconfig and bluetoothd. These utilities and updates
to Bluetooth kernel modules are provided in the BlueZ packages. For
more information, see <http://www.bluez.org/>.

source code:

net/bluetooth/