What exactly does this mean?  How does it not support any other type
of SPI peripheral?  SPI is a really simple protocol, so what is it
about this hardware that prevents it being used with other SPI
hardware?

I see a big state machine that appears to interpret the messages and
pretend to be an SPI slave instead of telling linux about the real
device.  /me wonders if it should this instead be a block device
driver?

Thomas will need to comment on this part

quoted

+static int falcon_sflash_prepare_xfer(struct spi_master *master)
+{
+	return 0;
+}
+
+static int falcon_sflash_unprepare_xfer(struct spi_master *master)
+{
+	return 0;
+}

Don't use empty hooks.  Just leave them uninitialized.  The core will
do the right thing.

I was under the impression that the need for these 2 callbacks was
removed in 3.5. As this patch flows via MIPS there would be a merge
order problem making the kernel non bisectable

I am a bit confused. You keep ack'ing this driver and then commenting on
it a few weeks later.... obsoleting the ACK ...