Add 3rdparty license information to the README

Signed-off-by: Aditya Deshpande <aditya.deshpande@arm.com>

README.md

@@ -305,6 +305,12 @@ License
 
 Unless specifically indicated otherwise in a file, Mbed TLS files are provided under the [Apache-2.0](https://spdx.org/licenses/Apache-2.0.html) license. See the [LICENSE](LICENSE) file for the full text of this license. Contributors must accept that their contributions are made under both the Apache-2.0 AND [GPL-2.0-or-later](https://spdx.org/licenses/GPL-2.0-or-later.html) licenses. This enables LTS (Long Term Support) branches of the software to be provided under either the Apache-2.0 OR GPL-2.0-or-later licenses.
 
+### Other Projects
+This project contains code from other projects. This code is located within the `3rdparty/` directory. The original license text is included within project subdirectories, and in source files. The projects are listed below:
+
+* `3rdparty/everest/`: Files stem from [Project Everest](https://project-everest.github.io/) and are distributed under the Apache 2.0 license.
+* `3rdparty/p256-m/p256-m/`: Files have been taken from the [p256-m](https://github.com/mpg/p256-m) repository. The code in the original repository is distributed under the Apache 2.0 license. It is also used by the project under the Apache 2.0 license.
+
 Contributing
 ------------