ci: add README for lava test plans

This commit adds README.md describing the usage and constraints of the
test job templates in ci/lava directory.

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@oss.qualcomm.com>

Author: mwasilew

ci/lava/README.md

@@ -0,0 +1,36 @@
+# Test setup
+
+`ci/lava` directory contains directories with names corresponding to build MACHINE names.
+New directories should only be added after the build is available for a given MACHINE.
+All files in the `ci/lava/<MACHINE>` directory should have `.yaml` extension.
+Each file should be a valid LAVA job template.
+
+LAVA templates are used to create test jobs during the CI runs in this repository.
+This happens for the following triggers:
+ - pull_request
+ - push
+ - cron (nightly build)
+
+# LAVA job templates
+
+Job templates can use the following variables:
+ - `DEVICE_TYPE`: name of the LAVA device type or alias. Full list can be found on [LAVA master web interface](https://lava.infra.foundries.io/scheduler/device_types)
+ - `GITHUB_SHA`: Commit ID corresponding to the github action trigger
+ - `BUILD_FILE_NAME`: Name of the build artifact to be downloaded. It's constructed as: `core-image-base-${DEVICE_TYPE}.rootfs.qcomflash.tar.gz`
+ - `BUILD_DOWNLOAD_URL`: URL where the build artifacts can be found. This variable is constructed as: `${{inputs.url}}/${DEVICE_TYPE}/${BUILD_FILE_NAME}` where `{{inputs.url}}` comes from the build action.
+ - `GITHUB_RUN_ID`: ID of the current Github run.
+
+After variable substitution the file should form a valid LAVA job definition.
+
+# Template validation
+
+Template validation is performed as github action using `lavasoftware/lava-server` container.
+Version of the container will be kept in sync with the LAVA server running the test jobs.
+Validation script, `schemacheck.py`, uses LAVA code from `lava_common.schemas.validate` method and PyYAML parser.
+
+## Local template validation
+
+Before checking the schema locally, all variables mentioned above need to be substituted.
+Templates can be validated using `lavasoftware/lava-server` container.
+
+    docker run --rm -v $PWD:/home/ lavasoftware/lava-server:latest python3 /home/ci/schemacheck.py /home/ci/lava