On the page DW1000 - Qorvo
follow the link
DW1000 API with STM32F10x Application Examples
Rev 2p14
In the zip file that gives the core of the driver is in dw1000_api_rev2p14_stsw.zip\dw1000_api_rev2p14_stsw\Src\decadriver\deca_device_api.h and deca_device.c
That directory and the dw1000_api_rev2p14_stsw.zip\dw1000_api_rev2p14_stsw\Src\platform directory contain all the decawave specific driver files.