license: use SPDX identifiers for src/ headers (#3749)

* license: use SPDX identifiers for src/ headers

Replace the full ~20-line MIT license boilerplate on every src/ file with a
two-line SPDX tag (SPDX-FileCopyrightText + SPDX-License-Identifier), following
the REUSE convention used by CircuitPython and the Linux kernel. Removes ~3500
lines of duplicated boilerplate.

1 files changed, 21 insertions, 0 deletions

diff --git a/LICENSES/MIT.txt b/LICENSES/MIT.txt
new file mode 100644
index 000000000..242da6233
--- /dev/null
+++ b/LICENSES/MIT.txt
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) <year> <copyright holders>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.