Device tree overlay sources not in /lib/firmware on Debian?

Hey all, sorry if this is a common question but are the .dts device tree overlay source files not put in /lib/firmware with Debian for a reason? I found a few installed in random places like /opt/source but just wanted to make sure I’m not missing something obvious.

If they’re not there by design, is there a package or easy way to install them? It seems like it would be really handy to have the source files since a lot of tutorials and blog posts about using the device tree mention the source files from /lib/firmware (did Angstrom put the source files there?).