softdevice handler.h is missing

I want to use 

softdevice_sys_evt_handler_set()
  it should be implemented in sofdevice_handler.h but this file does not exist in any of my directories. I am using sdk 14.2.0

However, i have nrf_sdh.h which has  equivalent functions to those in the missing file.

How can I substitute softdevice_sys_evt_handler_set() I have went through the file but I can#t understand how can I do so.

Any help