[PATCH] sh: maple: Add support for VMU devices (v2) [0/3]

[Adrian McMenamin]

This series of patches adds support for the Dreamcast Visual Memory
Unit, reworking the maple bus code to ensure it supports asynchronous
reads and writes. A consequential amendment to the keyboard driver is
also included.

The VMU is a 'smart' flash chip where access is controlled by a
microcontroller so that, for instance, flash erases appear to be
transparent to the end user. The VMU does, however, show typical
flash-type behaviour (eg phased writes) and the MTD layer and the chip
work well together (eg in the way they handle apparent hotplug events
during a block write).

Signed-off-by: Adrian McMenamin <adrian at mcmen.demon.co.uk>
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