doc: trivial: Quick revision of README

I took a quick look and felt like it wasn't clearly demonstrating
current state, so decided to revise the text. It should be more
clear now as to the state of reality.

Change-Id: I1b3c808f6d75e1e7fa532d18df82418a4747071a
Signed-off-by: Julia Kreger <juliaashleykreger@gmail.com>

README.rst

@@ -9,10 +9,20 @@ Overview
 
 Ironic consists of an API and plug-ins for managing and provisioning
 physical machines in a security-aware and fault-tolerant manner. It can be
-used with nova as a hypervisor driver, or standalone service using bifrost.
-By default, it will use PXE and IPMI to interact with bare metal machines.
-Ironic also supports vendor-specific plug-ins which may implement additional
-functionality.
+used with nova as a hypervisor driver, or standalone service.
+
+By default, it will use PXE and IPMI/Redfish to interact with bare metal
+machines. Some drivers, like the Redfish drivers, also support advanced
+features like leveraging HTTPBoot or Virtual Media based boot operations
+depending on the configuration by the user. Ironic also supports
+vendor-specific plug-ins which may implement additional functionality,
+however many vendors have chosen to focus on their Redfish implementations
+instead of customized drivers.
+
+Numerous ways exist to leverage Ironic to deploy a bare metal node, above
+and beyond asking Nova for a "bare metal" instance, or for asking Ironic
+to manually deploy a specific machine. Bifrost and Metal3 are related
+projects which seek to simplify the use and interaction of Ironic.
 
 Ironic is distributed under the terms of the Apache License, Version 2.0. The
 full terms and conditions of this license are detailed in the LICENSE file.