/lib/firmware is a volatile directory in a ramdisk and re-created on every boot.
If you want to permanently add firmware files create a /storage/.config/firmware/ directory and put the files there, then reboot.
so long,
Hias
Great HiassofT, it's work.
I use this firmware to filtering subwoofer output:
GitHub - allocom/piano-firmware: Allo Piano HiFi DAC DSP firmware files
Thank You very much