README: Add section addressing motherboard-support FAQ

This is a common enough question on Discord that we should probably make
it easier for people to find the answer themselves (or at least have an
easy thing to refer people to when it inevitably arises anyway).

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Change-Id: I54757f0902bfedca86d41cab0fc55b39cb7dfc1e

README.md

@@ -138,6 +138,34 @@ For technical discussions, please see [contact info](#contact) below for Discord
 and mailing list information. Please don't file an issue to ask a question.
 You'll get faster results by using the mailing list or Discord.
 
+### Will OpenBMC run on my Acme Server Corp. XYZ5000 motherboard?
+
+This is a common question, particularly regarding boards from popular COTS
+(commercial off-the-shelf) vendors such as Supermicro and ASRock.  You can see
+the list of supported boards by running `. setup` (with no further arguments) in
+the root of the OpenBMC source tree.  Most of the platforms supported by OpenBMC
+are specialized servers operated by companies running large datacenters, but
+some more generic COTS servers are supported to varying degrees.
+
+If your motherboard is not listed in the output of `. setup` it is not currently
+supported.  Porting OpenBMC to a new platform is a non-trivial undertaking,
+ideally done with the assistance of schematics and other documentation from the
+manufacturer (it is not completely infeasible to take on a porting effort
+without documentation via reverse engineering, but it is considerably more
+difficult, and probably involves a greater risk of hardware damage).
+
+**However**, even if your motherboard is among those listed in the output of
+`. setup`, there are two significant caveats to bear in mind.  First, not all
+ports are equally mature -- some platforms are better supported than others, and
+functionality on some "supported" boards may be fairly limited.  Second, support
+for a motherboard is not the same as support for a complete system -- in
+particular, fan control is critically dependent on not just the motherboard but
+also the fans connected to it and the chassis that the board and fans are housed
+in, both of which can vary dramatically between systems using the same board
+model.  So while you may be able to compile and install an OpenBMC build on your
+system and get some basic functionality, rough edges (such as your cooling fans
+running continuously at full throttle) are likely.
+
 ## Features of OpenBMC
 
 ### Feature List