I tried building the mainline kernel (ayufan) for NanoPC T4. My aim is to bring up bluetooth. No quite familiar with device tree, just googling and reading the kernel doc, and now I had some luck.   According to this post (https://discuss.96boards.org/t/updated-preliminary-support-for-bluetooth-in-debian-rock960/5588/7) in 96boards forum, in recent kernel, there is a serial bus support for bcm blutooth.   ----   firmware. I used firmware from the repo mentioned in t