diff --git a/llvm/docs/GitHub.rst b/llvm/docs/GitHub.rst
--- a/llvm/docs/GitHub.rst
+++ b/llvm/docs/GitHub.rst
@@ -12,6 +12,17 @@
 This page describes how the LLVM Project users and developers can
 participate in the project using GitHub.
 
+Branches
+========
+Do not create any branches in the llvm/llvm-project repository.  This repository
+is reserved for official project branches only.  We may relax this rule in
+the future if needed to support "stacked" pull request, but in that case only
+branches being used for "stacked" pull requests will be allowed.
+
+For pull requests, please push a branch to your fork of the llvm-project and
+`create a pull request from the fork <https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request-from-a-fork>`_.
+
+
 Releases
 ========