Document requirements for BIOS and RAID configuration

Ideally we will fix these issues, but documenting them is a good first
step.

Change-Id: I9a840005d62b974f0681ac39e1ff02ae3ff0120e
Story: 2004967
Task: 29410

doc/source/deployment.rst

@@ -285,6 +285,11 @@ BIOS and RAID Configuration
    BIOS and RAID configuration may require one or more power cycles of the
    hardware to complete the operation.  These will be performed automatically.
 
+.. note::
+
+   Currently, BIOS and RAID configuration of overcloud hosts is supported for
+   Dell servers only.
+
 Configuration of BIOS settings and RAID volumes is currently performed out of
 band as a separate task from hardware provisioning.  To configure the BIOS and
 RAID::
@@ -297,6 +302,14 @@ properties and root device hints.  To perform manual hardware inspection::
 
     (kayobe) $ kayobe overcloud hardware inspect
 
+There are currently a few limitations to configuring BIOS and RAID:
+
+* The Ansible control host must be able to access the BMCs of the servers being
+  configured.
+* The Ansible control host must have the ``python-dracclient`` Python module
+  available to the Python interpreter used by Ansible. The path to the Python
+  interpreter is configured via ``ansible_python_interpreter``.
+
 Provisioning
 ------------