These files are mainly created to support the Open Build Service, with the debtransform tool.
For example:
$ mkdir outdir
$ perl ./debtransform --changelog debian.changelog --release 0.3.0-1 . rizin.dsc outdir
If you want to build for an older version of Debian/Ubuntu that required special patches, you can use a different .dsc file:
$ mkdir outdir
$ perl ./debtransform --changelog debian.changelog --release 0.3.0-1 . rizin-Debian_10.dsc outdir