README: Add link to ipmi_flash state machine doc

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ib45bc52614b70d394bf66c76be9fa3ac9104a18f
diff --git a/README.md b/README.md
index 5af6f97..b6cb80a 100644
--- a/README.md
+++ b/README.md
@@ -105,3 +105,10 @@
 `VERIFY_STATUS_FILENAME`     | `/tmp/bmc.verify`          | The file checked for the verification status.
 `VERIFY_DBUS_SERVICE`        | `verify_image.service`     | The systemd service started for verification.
 `UPDATE_DBUS_SERVICE`        | `update-bmc.service`       | The systemd service started for updating the BMC.
+
+## Flash State Machine Details
+
+[This document](ipmi_flash.md) describes the details of the state machine
+implemented and how differnet interactions with it will respond.  This also
+describes how a host-side tool is expected to talk to it (triggering different
+states and actions).