documentation: Add repository diff control file

Add `documentation/repos-diff-control.md` file to manage
difference with https://github.com/arduino/ArduinoCore-zephyr.

Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>

Author: soburi

documentation/repos-diff-control.md

@@ -0,0 +1,71 @@
+# Repository diff control
+
+This file tracks how it handled the differences that arise when merging with
+https://github.com/arduino/ArduinoCore-zephyr.
+
+## Excluded because of license incompatibility.
+
+* `libraries/Arduino_LED_Matrix/`
+* `libraries/Camera/`
+* `libraries/Ethernet/`
+* `libraries/RTC/`
+* `libraries/SocketWrapper/`
+* `libraries/Storage/`
+* `libraries/WiFi/`
+* `libraries/Zephyr_SDRAM/`
+* `libraries/ea_malloc/`
+* `loader/blobs/`
+* `tools/sync-zephyr-artifacts/`
+* `boards.txt`
+* `platform.txt`
+* `post_install.sh`
+* `programmers.txt`
+
+## Excluded due to repository configuration differences
+
+* `.github/ISSUE_TEMPLATE/compilation_bug_report.md`
+* `.github/ISSUE_TEMPLATE/miscellaneous_bug_report.md`
+* `.github/ISSUE_TEMPLATE/runtime_bug_report.md`
+* `.github/workflows/commit_check.yml`
+* `.github/workflows/leave_pr_comment.yml`
+* `.github/workflows/package_core.yml`
+* `.github/workflows/package_tool.yml`
+* `.github/workflows/report_size_deltas.yml`
+* `.github/workflows/scancode.yml`
+* `.github/workflows/upload_json.yml`
+* `.gitmodules`
+* `cores/arduino/api`
+
+## Keep the original for now because integration is not yet complete
+
+- [ ] `.github/`
+- [ ] `README.md`
+- [ ] `Kconfig`
+- [ ] `CMakeLists.txt`
+- [ ] `cores/CMakeLists.txt`
+- [ ] `cores/arduino/CMakeLists.txt`
+- [ ] `cores/arduino/Arduino.h`
+- [ ] `cores/arduino/main.cpp`
+- [ ] `cores/arduino/zephyrPrint.cpp`
+- [ ] `cores/arduino/zephyrPrint.h`
+- [ ] `cores/arduino/zephyrSerial.cpp`
+- [ ] `cores/arduino/zephyrSerial.h`
+- [ ] `documentation/variants.md`
+- [ ] `libraries/SPI`
+- [ ] `libraries/Wire`
+- [ ] `samples`
+- [ ] `variants/default/variant.h`
+- [ ] `west.yml`
+
+
+### Bump to 0.55.0
+
+- Add SPDX-Identifier
+  - [x] `variants/arduino_nano_33_ble/arduino_nano_33_ble.overlay`
+  - [x] `variants/arduino_nano_33_iot/arduino_nano_33_iot.overlay`
+  - [x] `variants/nrf52840dk_nrf52840/nrf52840dk_nrf52840.overlay`
+  - [x] `variants/nrf9160dk_nrf9160/nrf9160dk_nrf9160.overlay`
+
+- Add CAN library
+  - [x] `libraries/CMakeLists.txt`
+