DEVELOPING: Engage Redfish before adding OEM

Added a Redfish section about engaging the DMTF's Redfish working group
before adding a Redfish OEM schema or property.

See https://lists.ozlabs.org/pipermail/openbmc/2019-November/019571.html

Tested: https://jbt.github.io/markdown-editor/ and grammarly.com
Change-Id: I946483a90e34f63930a2cba047d14226d2da7583
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/DEVELOPING.md b/DEVELOPING.md
index 3562d9c..b8a2a26 100644
--- a/DEVELOPING.md
+++ b/DEVELOPING.md
@@ -113,7 +113,20 @@
    the required flows to host the application.  In general, all access methods
    should be available to the webui.
 
-12. ### Developing and Testing
+12. ### Redfish
+   bmcweb's Redfish implementation, including Redfish OEM Resources, shall
+   conform to the Redfish specification. Please keep bmcweb's [Redfish support
+   document](https://github.com/openbmc/bmcweb/blob/master/Redfish.md) updated.
+   Before adding a Redfish OEM schema or property first engage the DMTF's
+   Redfish working group to see if they are interested in adding the new
+   feature. The [Redfish Specification Forum](https://redfishforum.com/) is a
+   public Redfish forum to ask questions and request features. Redfish
+   "Supporter" and "Promoter" companies, which many companies working on OpenBMC
+   are, can request features via the Redfish code repository or via Redfish
+   meetings. For more information on Redfish and supported schemas visit
+   [Redfish.md](https://github.com/openbmc/bmcweb/blob/master/Redfish.md).
+
+13. ### Developing and Testing
   There are a variety of ways to develop and test bmcweb software changes.
   Here are the steps for using the SDK and QEMU.