Update readme with component location

This patch adds a small section to the README.md with the locations that
the different openstack components need to look into to ensure that they
are gathering the information they want from the control plane in the
customer cases.

README.md

@@ -94,6 +94,26 @@ sh-5.1# gather
 sh-5.1# rm /tmp/rm-to-finish-gathering
 ```
 
+### Component specifics
+
+Besides the generic OpenShift etcd objects that must-gather scripts are
+currently gathering there's also component specific code that gather other
+information, so when adding or improving a component we should look into:
+
+- `collection-scripts/common.sh`: Services are in the `OSP_SERVICES` variable
+  to indicate that the script must gather its config maps, secrets, additional
+  information, trigger Guru Mediation Reports, etc.
+
+- `collection-scripts/gather_services_status`: Runs OpenStack commands to
+  gather additional information. For example for Cinder it gather state of the
+  services, volume types, qos specs, volume transfer requests, summary of
+  existing volumes, pool information, etc.
+
+- `collection-scripts/gather_trigger_gmr`: Triggers Guru Meditation Reports on
+  the services so they are present in the logs when those are gathered
+  afterwards.
+
+
 ## Example
 
 (optional) Build and push the must-gather image to a registry: