How does Postgres support backwards compatibility

Hello Everyone,

I work on an extension for Postgres. We originally developed the extension
for Postgres 11. Now we are looking into supporting newer versions of
Postgres. We would like our extension to be compatible with multiple
versions of Postgres. Is there a document that explains how the Postgres
community handles releases and supports older versions? Any information on
how Postgres handles this will give us guidance on how to best approach
this subject.

Thank You.