Add branch strategy to README

README.md

@@ -60,6 +60,16 @@ This repository consists of these files and directories (partial):
 - `mkdocs.yml` - MkDocs recipe for the spec documentation generation. The
   inclusion of model files and the order of chapters are defined here.
 
+## Branch structre
+
+The SPDX spec repo follows the [Gitflow](https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow) workflow with the addition of support branches.
+
+The branches in use are:
+- main - This will always be the latest released specification.
+- develop - This branch will be where the active development for the next major or minor version will take place.  Once relased, the develop branch will be merged into the main branch.
+- support/x.y - These branches will be long lived and contain any updates to a minor version of the specification.  Additions such as translations can be added to the support branch.  x.y represents the major/minor version.  Once any changes are accepted and released, the support branch will be tagged and merged into both the develop and main branches.
+- general feature or fix branches - there may be feature branches made for specific enhancements or fixes to the spec.  These will be short lived and merged into either a support branch or the develop branch.
+
 ## Related documents and repositories
 
 | Documentation | Link |