I2C4 enable

I am using debian 9.9 OS.

The BBX15 board has an i2c4 port on P17 expansion header.

If i run i2cdetect -l from /dev folder, i can see only i2c0 and i2c2. So i guess I2C4 which is available on P17 expansion header is not enabled?
What is the procedure to enable it.

Do i have to use the device tree source file for this? If yes, can some help be provided regarding how to tweak the dts file to add entry for i2c4.

Also where is the .dts file for BBX15 located?

Thanks in advance.Any suggestions will be greatly appreciated.