diff --git a/docs/HOW_MBS_BUILDS_MODULES.rst b/docs/HOW_MBS_BUILDS_MODULES.rst
index daa88d7b..bfac0231 100644
--- a/docs/HOW_MBS_BUILDS_MODULES.rst
+++ b/docs/HOW_MBS_BUILDS_MODULES.rst
@@ -11,13 +11,27 @@ User submits module build request
 
 There is the MBS frontend, which provides a REST API (See ``views.py``). A user sends a POST request
 with JSON describing the module to build. There is mainly the URL to the git repository (called
-``scmurl``) and branch name (called ``branch``). The ``scmurl`` points to the git repository containing
-the modulemd file defining the module.
+``scmurl`` |---| which points to the git repository containing the modulemd file defining the module)
+and branch name (called ``branch``).
 
 This JSON data is handled by ``views.SCMHandler``, which validates the JSON and calls
 ``utils.submit.submit_module_build_from_scm(...)`` method. This goes down to
 ``submit_module_build(...)``.
 
+Alternatively, if submitting a YAML modulemd file is allowed (MBS setting
+``YAML_SUBMIT_ALLOWED`` is ``True``), the user can send a ``multipart/form-data``
+POST request directly including the contents of a YAML modulemd file
+(called ``yaml``). In this case, the JSON data and YAML file are handled by
+``views.YAMLFileHandler``, which validates the data and calls the
+``utils.submit.submit_module_build_from_yaml(...)`` method which also goes down
+to ``submit_module_build(...)``.
+
+If module scratch builds are allowed (MBS setting ``MODULE_ALLOW_SCRATCH`` is
+``True``), the user can also upload one or more source RPMs uploaded to Koji
+via calls to Koji's ``session.uploadWrapper(..)``, and supply the list of
+upload links to MBS (called ``srpms``). Such custom SRPMs will be used to
+override the git repository source for corresponding components.
+
 
 Module Stream Expansion (MSE)
 -----------------------------
@@ -183,3 +197,6 @@ The "done" state message is handled in the ``scheduler.handlers.modules.done(...
 This method imports the module build into Koji using the ``KojiContentGenerator`` class.
 The module build in Koji points to the Koji tag with the module's components and also contains the
 final modulemd files generated for earch architecture the module is built for.
+
+.. |---| unicode:: U+2014  .. em dash, trimming surrounding whitespace
+   :trim: