If you know what devices you would like to add, we can start talking with precision
ok..... let's go step by step
I would add the following device:
A867 Sky ddt
in the file bm750_defconfig, must be added the following entry:CONFIG_DVB_USB_A867=m
correct ?
This is the LAST step.
First of all you should prepare (or adapt) one o more patches to add the driver into the kernel.
You can see OpenPli OE Git and BlackPole OE Git to take inspiration. In the second git, there are prepared patches for Vu+ boxes.