Merge pull request #6925 from gilles-peskine-arm/coding-style-doc

Switch to the new coding style: documentation
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index fc79e49..a7bf198 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -14,8 +14,8 @@
 
 Coding Standards
 ----------------
-- We would ask that contributions conform to [our coding standards](https://mbed-tls.readthedocs.io/en/latest/kb/development/mbedtls-coding-standards/), and that contributions are fully tested before submission, as mentioned in the [Tests](#tests) and [Continuous Integration](#continuous-integration-tests) sections.
-- The code should be written in a clean and readable style.
+- Contributions should include tests, as mentioned in the [Tests](#tests) and [Continuous Integration](#continuous-integration-tests) sections. Please check that your contribution passes basic tests before submission, and check the CI results after making a pull request.
+- The code should be written in a clean and readable style, and must follow [our coding standards](https://mbed-tls.readthedocs.io/en/latest/kb/development/mbedtls-coding-standards/).
 - The code should be written in a portable generic way, that will benefit the whole community, and not only your own needs.
 - The code should be secure, and will be reviewed from a security point of view as well.
 
diff --git a/ChangeLog.d/coding-style.txt b/ChangeLog.d/coding-style.txt
new file mode 100644
index 0000000..b2cff5c
--- /dev/null
+++ b/ChangeLog.d/coding-style.txt
@@ -0,0 +1,5 @@
+Changes
+   * The C code follows a new coding style. This is transparent for users but
+     affects contributors and maintainers of local patches. For more
+     information, see
+     https://mbed-tls.readthedocs.io/en/latest/kb/how-to/rewrite-branch-for-coding-style/