Mention where LLVM commits should go to in the branches document

Author: hyp

docs/Branches.md

@@ -56,7 +56,13 @@ You can use any of the branch names as the argument to `--scheme`, such as `mast
 
 - Swift: new commits go to `master`
 
-- LLVM Project: new commits go to `swift/master-next`
+- LLVM Project (Non-lldb commits): New commits go to `master` in the upstream [llvm-project](https://github.com/llvm/llvm-project).
+
+  ... then these commits can be cherry-picked to an appropriate, `swift/master` aligned `apple/stable/*` branch in Apple's fork of [llvm-project](https://github.com/apple/llvm-project). Please see
+  [Apple's branching scheme](https://github.com/apple/llvm-project/blob/apple/master/apple-docs/AppleBranchingScheme.md)
+  document to determine which `apple/stable/*` branch you should cherry-pick to.
+
+- LLVM Project (LLDB commits): new commits go to `swift/master-next`
 
 ...then cherry-pick to the release branch (`swift/swift-x.y-branch`) if necessary, following the appropriate release process. (Usually this means filling out a standard template, finding someone to review your code if that hasn't already happened, and getting approval from that repo's *release manager.)*