FMC: add a software mezzanine driver

This simple do-nothing mezzanine driver shows how to write a mezzanine
driver, that can also handle interrupts reported by the carrier.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
Acked-by: Juan David Gonzalez Cobas <dcobas@cern.ch>
Acked-by: Emilio G. Cota <cota@braap.org>
Acked-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/fmc/fmc-trivial.txt b/Documentation/fmc/fmc-trivial.txt
new file mode 100644
index 0000000..d1910bc
--- /dev/null
+++ b/Documentation/fmc/fmc-trivial.txt
@@ -0,0 +1,17 @@
+fmc-trivial
+===========
+
+The simple module fmc-trivial is just a simple client that registers an
+interrupt handler. I used it to verify the basic mechanism of the FMC
+bus and how interrupts worked.
+
+The module implements the generic FMC parameters, so it can program a
+different gateware file in each card. The whole list of parameters it
+accepts are:
+
+`busid='
+`gateware='
+     Generic parameters. See mezzanine.txt
+
+
+This driver is worth reading, in my opinion.