On Wed, 21 Mar 2012 23:38:11 +0100, Sylwester Nawrocki [off-list ref] wrote:

Hello,

I'm working on adding the device tree support for two devices that
share some IO registers. Exactly, there is one shared SFR that 
contains a common bit to enable two PHY devices, and another two
bits, each to separately reset each PHY.

Currently this shared register is statically memory mapped and it is
handled by a platform specific callback, that both drivers use to
control their corresponding (sub)devices in synchronised manner.

The two devices are a MIPI-CSI2 receiver and a MIPI-DSI transmitter, 
and the common register is there to control the camera and the display 
port PHY. The hardware design is a bit unfortunate, but there is not
much I could do about it.

Generally, this is handled by having a third node for the shared
register block and both device nodes holding a phandle to it.

No, there isn't any common infrastructure for implementing this, but
it isn't very much code.

g.