dt-bindings: bus: Add Baikal-T1 AXI-bus binding

dt-bindings: bus: Add Baikal-T1 AXI-bus binding

AXI3-bus is the main communication bus connecting all high-speed
peripheral IP-cores with RAM controller and with MIPS P5600 cores on
Baikal-T1 SoC. This binding describes the DW AMBA 3 AXI Inteconnect
and Errors Handler Block synthesized on top of it, which are
responsible for the AXI-bus traffic arbitration and errors reporting
upstream to CPU. Baikal-T1 AXI-bus DT node is supposed to be compatible
with "be,bt1-axi" and "simple-bus" drivers, should have reg property with
AXI-bus QOS registers space, syscon phandle reference to the Baikal-T1
System Controller, IRQ line declared, AXI Interconnect reference clock and
reset line.

Link: https://lore.kernel.org/r/20200526125928.17096-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: linux-mips@vger.kernel.org
Cc: soc@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>