Add 'doc/' from commit 'bebd681c7be7caf016ad8206bd744b58bb8d7baa'

git-subtree-dir: doc
git-subtree-mainline: bebd681c7be7caf016ad8206bd744b58bb8d7baa
git-subtree-split: bebd681c7be7caf016ad8206bd744b58bb8d7baa
Initialize