This patch implements the remote I2C device.
The remote I2C device allows an external I2C device to communicate with the I2C controller in QEMU through the remote I2C protocol.
Users no longer have to directly modify QEMU to add new I2C devices and can instead implement the emulated device externally and connect it to the remote I2C device.

Previous work by Wolfram Sang (https://git.kernel.org/pub/scm/virt/qemu/wsa/qemu.git/commit/?h=i2c-passthrough) was referenced.
It shares the similar idea of redirecting the actual I2C device functionalities, but Sang focuses on physical devices, and we focus on emulated devices.
The work by Sang mainly utilizes file descriptors while ours utilizes character devices, which offers better support for emulated devices.
The work by Sang is not meant to offer full I2C device support; it only implements the receive functionality.
Our work implements full support for I2C devices: send, recv, and event (match_and_add is not applicable for external devices).

Shengtan Mao (1):
  hw/i2c: add remote I2C device

 hw/arm/Kconfig                |   1 +
 hw/i2c/Kconfig                |   4 +
 hw/i2c/meson.build            |   1 +
 hw/i2c/remote-i2c.c           | 117 ++++++++++++++++++
 tests/qtest/meson.build       |   1 +
 tests/qtest/remote-i2c-test.c | 216 ++++++++++++++++++++++++++++++++++
 6 files changed, 340 insertions(+)
 create mode 100644 hw/i2c/remote-i2c.c
 create mode 100644 tests/qtest/remote-i2c-test.c

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2.32.0.402.g57bb445576-goog