Doc: IBM flashsystem driver update
Updated the name as 'IBM FlashSystem 840/900 driver'
to avoid confusion with other flash system models which is
part of IBM Spectrum Virtualize Family driver.
-=============================
-IBM FlashSystem volume driver
-=============================
+==============================
+IBM FlashSystem 840/900 driver
+==============================
The volume driver for FlashSystem provides OpenStack Block Storage hosts
with access to IBM FlashSystems.
+This driver is to be used with IBM FlashSystem 840/900 systems only.
+For any other FlashSystem storage systems (including 5xxx, 7xxx, and 9xxx
+platforms) see the :doc:`IBM Spectrum Virtualize family volume driver
+documentation <ibm-storwize-svc-driver>`.
+
Supported operations
~~~~~~~~~~~~~~~~~~~~
