How to upstream Broadcom WiFi firmware files?

Hi,

We have Android devices that are well supported by upstream kernel and
other upstreams. The biggest missing part is the WiFi firmware files of
Broadcom chips, which don't work using stock binary firmware provided by
linux-firmware package. We need per-board firmware files for them. The
NVRAM configs are also missing. The main problem is that the license of
those firmware files is unknown, the NVRAM files have copyrights and
that's it. The devices in question are nearly 10 years old and are long
time unsupported by vendors. Is it possible to upstream those firmware
files and how it can be done?