[PATCHv2] doc: Add basic information about running CI tests

[Tom Rini <trini@konsulko.com>]

Start out by documenting general expectations on when CI is run, how
anyone can run Azure pipelines, and how GitLab CI pipelines can be run.

Signed-off-by: Tom Rini <trini@konsulko.com>
---
Changes in v2:
- Address some of Akashi-san's feedback
---
 doc/develop/ci_testing.rst | 45 ++++++++++++++++++++++++++++++++++++++
 doc/develop/index.rst      |  1 +
 2 files changed, 46 insertions(+)
 create mode 100644 doc/develop/ci_testing.rst

diff --git a/doc/develop/ci_testing.rst b/doc/develop/ci_testing.rst
new file mode 100644
index 000000000000..48dbec4a4452
--- /dev/null
+++ b/doc/develop/ci_testing.rst
@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Continuous Integration testing
+==============================
+
+All changes require passing our continuous integration tests prior to being
+merged in to mainline.  To help facilitate merges being accepted quickly,
+custodians are encouraged but not required to run a pipeline prior to sending a
+pull request.  Individual developers submitting significant or widespread
+changes are encouraged to run a pipeline themselves prior to posting.
+
+In order to make this process as easy as possible, the ability to run a CI
+pipeline is provided in both Azure and GitLab.  Both of these pipelines perform
+their Linux build jobs on the same Docker container image.
+
+Azure Pipelines
+---------------
+
+Currently there are two ways to run a Microsoft Azure Pipeline test for U-Boot.
+The first way is to create an account with Microsoft at
+https://azure.microsoft.com/en-us/services/devops/ and then use the
+``.azure-pipelines.yml`` file in the U-Boot repository as the pipeline
+description.  The second way is to use GitHub and submit a pull request against
+https://github.com/u-boot/u-boot as this will trigger an Azure pipeline run.
+Clicking on your pull request on the list at
+https://github.com/u-boot/u-boot/pulls and then the "Checks" tab will show the
+results.
+
+GitLab CI Pipelines
+-------------------
+
+Currently, we support running GitLab CI pipelines only for custodians, due to
+the resources the project has available.  For Custodians, it is a matter of
+enabling the pipeline feature in your project repository following the standard
+GitLab documentation.  For non-custodians, the pipeline itself is part of the
+tree and should be able to be used on any GitLab instance, with whatever
+runners you are able to provide.
+
+Docker container
+----------------
+
+As previously states, both of the above pipelines build using the same Docker
+container image.  This is maintained in the repository at
+https://gitlab.denx.de/u-boot/gitlab-ci-runner and new images are made as
+needed to support new tests or features.
diff --git a/doc/develop/index.rst b/doc/develop/index.rst
index 54e14dd77b5e..3c0f2da44318 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -9,6 +9,7 @@ Implementation
 .. toctree::
    :maxdepth: 1
 
+   ci_testing
    commands
    driver-model/index
    global_data
-- 
2.17.1