dt-bindings: bus: Minimal TI sysc interconnect target module binding

With the recently introduced omap clkctrl module binding, we can start
moving omap hwmod data to device tree and drivers from arch/arm/mach-omap2.

To start doing this, let's introduce a device tree binding for TI
sysc interconnect target module hardware. The sysc manages module clocks,
idlemodes and interconnect level resets. Each interconnect target module
can have one or more child devices connected to it.

TI sysc interconnect target module hardware is independent of the
interconnect. It is used at least with TI L3 interconnect (Arteris NoC)
and TI L4 interconnect (Sonics s3220). The sysc is mostly used for
interaction between module and PRCM. It participates in the OCP Disconnect
Protocol but other than that is mostly indepenent of the interconnect.

As all the features may not be supported for a given sysc module, we
need to use device tree configuration for the revision of the interconnect
target module.

Note that the interconnect target module control registers are always
sprinked at varying locations in the unused address space of the first
child device IP block. To avoid device tree reg conflicts, the sysc device
provides ranges for it's children.

For a non-intrusive transition from static hwmod data to using device
tree defined TI interconnect target module binding, we can keep things
working with static hwmod data if device tree property "ti,hwmods" is
specified for the the interconnect target module.

Note that additional properties for sysc capabilities will be added
later on. For now, we can already use this binding for interconnect
target modules that do not have any child device drivers available.
This allows us to idle the unused interconnect target modules during
init without the need for legacy hwmod platform data for doing it.

Cc: Benoît Cousson <bcousson@baylibre.com>
Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Matthijs van Duin <matthijsvanduin@gmail.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: Suman Anna <s-anna@ti.com>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>