docs(license): add third-party components and attributions

List the files written by third parties (Teensyduino, Daniel Fekete,
Bumsik Kim, Bjoern Hartmann, Arduino, Mentor Graphics, Xilinx) with
their copyright holder and license, so the notices to retain are
easy to find.
Mention the Arm CMSIS, CMSIS-DSP and CMSIS-NN packages, which are
Apache-2.0 licensed and downloaded as tools instead of being shipped
in this repository.

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>
Assisted-by: GitHub Copilot

Author: fpistm

License.md

@@ -67,6 +67,31 @@ This files includes licensing information for parts of this repository.
 > OpenAMP development scripts, licensed under GPLv2 (see its header). It is not
 > part of the build of the core.
 
+## Third-party components and attributions
+
+The following files are not written by STMicroelectronics or by the
+STM32duino contributors. The copyright notice and the permission notice of their
+header must be retained:
+
+| Files | Copyright | License |
+|-------|-----------|---------|
+| `libraries/SrcWrapper/src/new.cpp` | PJRC.COM, LLC (Teensyduino) | [MIT](#mit-license) |
+| `libraries/SrcWrapper/*/HardwareTimer.*` | Daniel Fekete (and STMicroelectronics) | [MIT](#mit-license) |
+| `libraries/VirtIO/*/virtio*`, `libraries/VirtIO/*/VirtIOSerial.*` | Bumsik Kim | [MIT](#mit-license) |
+| `cores/arduino/api/Udp.h` | Bjoern Hartmann | [MIT](#mit-license) |
+| `cores/arduino/api/deprecated-avr-comp/avr/pgmspace.h` | Arduino LLC (based on Paul Stoffregen's work) | [MIT](#mit-license) |
+| `cores/arduino/api` | Arduino LLC | [LGPLv2.1](#lgplv21) |
+| `system/Middlewares/OpenAMP/open-amp` | Mentor Graphics Corporation and contributors | [BSD 3-Clause License](#bsd-3-clause-license) |
+| `system/Middlewares/OpenAMP/libmetal` | Xilinx Inc. and contributors | [BSD 3-Clause License](#bsd-3-clause-license) |
+
+The following components are not part of this repository, they are downloaded
+as Arduino tools packages (see `platform.txt`) and are licensed by Arm under the
+[Apache License](#apache-license):
+
+* CMSIS (`CMSIS`)
+* CMSIS-DSP (`CMSIS_DSP`), also used by `libraries/CMSIS_DSP`
+* CMSIS-NN (`CMSIS_NN`)
+
 -------------------------------------------------------------------------------
 ## LGPLv2.1
                   GNU LESSER GENERAL PUBLIC LICENSE