docs: add repository README

README.md

@@ -1 +1,59 @@
-# Serial
+# C++ Bindings for Linux
+
+[![Build](https://github.com/Serial-IO/cpp-bindings-linux/actions/workflows/build_binary.yml/badge.svg)](https://github.com/Serial-IO/cpp-bindings-linux/actions/workflows/build_binary.yml)
+[![JSR](https://jsr.io/badges/@serial/cpp-bindings-linux)](https://jsr.io/@serial/cpp-bindings-linux)
+
+Linux shared library for serial communication. It implements the
+[`cpp-core`](https://github.com/Serial-IO/cpp-core) interface and provides functions for discovering, opening,
+configuring, reading from, and writing to serial ports.
+
+## Requirements
+
+- Linux
+- Git
+- CMake 3.30 or newer
+- Ninja
+- A compiler with C++26 support (CI uses GCC 16)
+
+CMake downloads `cpp-core` and GoogleTest automatically during configuration.
+
+## Build
+
+```sh
+git clone https://github.com/Serial-IO/cpp-bindings-linux.git
+cd cpp-bindings-linux
+cmake --preset linux-gcc-release
+cmake --build --preset linux-gcc-release --target cpp_bindings_linux
+```
+
+The shared library is written to `build/libcpp_bindings_linux.so`.
+
+To select a specific compiler, add it while configuring, for example:
+
+```sh
+cmake --preset linux-gcc-release \
+  -DCMAKE_C_COMPILER=gcc-16 \
+  -DCMAKE_CXX_COMPILER=g++-16
+```
+
+## Tests
+
+Build and run the C++ test suite:
+
+```sh
+cmake --build --preset linux-gcc-release --target cpp_bindings_linux_tests
+ctest --test-dir build --output-on-failure
+```
+
+Tests that require a serial device use `SERIAL_TEST_PORT`. They are skipped when no suitable device is available.
+
+The optional Deno FFI smoke tests require Deno 2 and a built library:
+
+```sh
+cd integration_tests
+deno task test
+```
+
+## License
+
+This project is licensed under the [GNU Lesser General Public License v3.0](LICENSE).