Document how to setup a new hardware runner

Signed-off-by: Victor Lira <VictorM.Lira@amd.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
v2: add external references and more examples

diff --git a/docs/misc/ci.rst b/docs/misc/ci.rst
index 7aee55c5d2..8d9ebfb39d 100644
--- a/docs/misc/ci.rst
+++ b/docs/misc/ci.rst
@@ -19,6 +19,55 @@ After getting access to relevant runners, few extra changes are necessary in set
 2. Expand "Variables" section and add ``QUBES_JOBS=true`` variable for Qubes runners.
 3. Go to Settings -> Repository, expand "Branch rules" section and add a rule for protected branches - only those branches will get tests on the hardware runners. It's okay to use a pattern for branch name, and it's okay to allow force push.
 
+How to Set Up a New Hardware Runner
+***********************************
+
+A hardware runner is a GitLab runner designed to execute Xen tests on real hardware, such as an embedded board or a laptop. The GitLab runner runs on a controller PC, which is connected to the target board used for Xen testing. The controller PC can be any system, from a workstation to a Raspberry Pi.
+
+Steps to Set Up the Controller PC:
+
+1. Install the Docker service
+   - Follow the instructions at: [Docker Installation Guide](https://docs.docker.com/engine/install/ubuntu/#install-using-the-repository)
+
+2. Install the GitLab Runner service
+   - Follow the instructions at: [GitLab Runner Installation Guide](https://docs.gitlab.com/runner/install/linux-repository/#install-gitlab-runner)
+
+3. Register the runner with GitLab
+   - Generate a runner token with a specific tag to identify it.
+   - Run `gitlab-runner register` and enter the token. Accepting the default settings is sufficient.
+
+These steps are common for setting up any GitLab runner. However, for hardware runners, additional configurations are required to enable the controller PC to:
+
+- Power on and off the target board.
+- Connect to the serial interface of the target board.
+- Establish an Ethernet connection with the target board.
+- Run a TFTP server with a TFTP root directory accessible by GitLab container tests.
+  - This allows the test script to place binaries, such as Xen, in the TFTP root before powering on the target board.
+
+To enable the required capabilities, edit the GitLab Runner configuration file located at `/etc/gitlab-runner/config.toml`:
+
+- Map the TFTP boot directory.
+- Map the serial device of the target board.
+
+Example Configuration:
+
+    volumes = ["/scratch/gitlab-runner:/scratch/gitlab-runner"]
+    devices = ["/dev/ttyUSB0:/dev/ttyUSB0"]
+
+After making these changes, restart the GitLab Runner service:
+
+    gitlab-runner restart
+
+This completes the setup of the hardware runner. The system is now ready for executing Xen tests on real hardware. As an example, to execute tests on an AMD x86 embedded board, we currently use the following script:
+
+    automation/scripts/xilinx-smoke-dom0-x86_64.sh
+
+Other examples are available under automation/scripts, such as
+automation/scripts/qubes-x86-64.sh, and at external locations:
+`<https://www.qubes-os.org/news/2022/05/05/automated-os-testing-on-physical-laptops>`_,
+`<https://github.com/QubesOS/tests-hw-setup/blob/28aa8b86208a54fc2ac986f06c66c92230bf771e/states/gitlab-runner-conf.toml>`_.
+
+
 Selecting individual tests
 **************************