-.. SPDX-License-Identifier: GPL-2.0
+.. This file is dual-licensed: you can use it either under the terms
+.. of the GPL 2.0 or the GFDL 1.1+ license, at your option. Note that this
+.. dual licensing only applies to this file, and not this project as a
+.. whole.
+..
+.. a) This file is free software; you can redistribute it and/or
+.. modify it under the terms of the GNU General Public License as
+.. published by the Free Software Foundation version 2 of
+.. the License.
+..
+.. This file is distributed in the hope that it will be useful,
+.. but WITHOUT ANY WARRANTY; without even the implied warranty of
+.. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+.. GNU General Public License for more details.
+..
+.. Or, alternatively,
+..
+.. b) Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
.. _encoder: