INTPYTHON-460 Documented supported versions and branch policy

Author: timgraham

docs/source/internals.rst

@@ -23,3 +23,42 @@ open an issue in our issue tracker, JIRA:
    the issue and the steps to reproduce it.
 
 Bug reports in JIRA for this project can be viewed by everyone.
+
+.. _supported-versions-policy:
+
+Supported versions
+==================
+
+Django MongoDB Backend follows Django's :ref:`supported versions policy
+<django:supported-versions-policy>`.
+
+The main development branch of Django MongoDB Backend follows the most recent
+:term:`django:feature release` of Django and gets all new features and
+non-critical bug fixes.
+
+Security fixes and data loss bugs will also be applied to the previous feature
+release branch, and any other supported long-term support release branches.
+
+As a concrete example, consider a moment in time between the release of Django
+5.2 and 6.0. At this point in time:
+
+- Features will be added to the main branch, to be released as Django 5.2.x.
+
+- Critical bug fixes will also be applied to the 5.1.x branch and released as
+  5.1.x, 5.1.x+1, etc.
+
+- Security fixes and bug fixes for data loss issues will be applied to main,
+  5.1.x, and any active LTS branches (e.g. 4.2.x, if Django MongoDB Backend
+  supported it). They will trigger the release of 5.2.x, 5.1.y, 4.2.z.
+
+.. _branch-policy:
+
+Branch policy
+=============
+
+After a new Django :term:`django:feature release` (5.2, 6.0, 6.1 etc.), Django
+MongoDB Backend's main branch starts tracking the new version following the
+merge of a "Add support for Django X.Y" PR. Before merging that PR, a branch is
+created off of main to track the previous feature release version. For example,
+the 5.1.x branch is created shortly after the release of Django 5.2, and main
+starts tracking the Django 5.2.x series.