(CONT-1200) - Add readme section for custom-matrix flag

README.md

@@ -37,7 +37,7 @@ How to use it: in the project module root directory run `bundle exec matrix_from
 
 ### --exclude-platforms parameter
 
-matrix_from_metadata_v2 accepts `--exclude-platforms <JSON array>` option in order to exclude some platforms from GA matrixes.
+matrix_from_metadata_v2 accepts the `--exclude-platforms <JSON array>` argument in order to exclude some platforms from GA matrixes.
 
 In order to use this new functionality just simply run:
 
@@ -46,6 +46,16 @@ In order to use this new functionality just simply run:
 > Note: The option value should be JSON string otherwise it will throw an error.
 > The values provided in the json array are case-insensitive `["debian-11","centos-8"]'` or `["Debian-11","CentOS-8"]'` are treated as being the same.
 
+### --custom-matrix parameter
+
+matrix_from_metadata_v2 accepts the `--custom-matrix /path/to/matrix.json` argument in order to execute your test suite against a custom matrix. This is useful for use cases that do not fit the default matrix generated.
+
+In order to use this new functionality, run:
+
+`$: bundle exec matrix_from_metadata_v2 --create-matrix matrix.json`
+
+> Note: The file should contain a valid Array of JSON Objects (i.e. `[{"label":"AlmaLinux-8","provider":"provision_service","image":"almalinux-cloud/almalinux-8"}, {..}]`), otherwise it will throw an error.
+
 ## Documentation
 
 For documentation, see our [Litmus Docs Site](https://puppetlabs.github.io/content-and-tooling-team/docs/litmus/).