arm64: dts: ti: k3-am65-mcu: Add MCU domain R5F cluster node

arm64: dts: ti: k3-am65-mcu: Add MCU domain R5F cluster node

The AM65x SoCs have a single dual-core Arm Cortex-R5F processor (R5FSS)
subsystem/cluster. This R5F cluster (MCU_R5FSS0) is present within the
MCU domain, and can be configured at boot time to be either run in a
LockStep mode or in an Asymmetric Multi Processing (AMP) fashion in
Split-mode. This subsystem has 64 KB each Tightly-Coupled Memory (TCM)
internal memories for each core split between two banks - TCMA and TCMB
(further interleaved into two banks). There are some IP integration
differences from standard Arm R5F clusters such as the absence of an ACP
port, presence of an additional TI-specific Region Address Translater
(RAT) module for translating 32-bit CPU addresses into larger system
bus addresses etc.

Add the DT node for this R5F cluster/subsystem, the two R5F cores are
added as child nodes to the main cluster node. The cluster is configured
to run in LockStep mode by default, with the ATCMs enabled to allow the
R5 cores to execute code from DDR with boot-strapping code from ATCM.
The inter-processor communication between the main A53 cores and these
processors is achieved through shared memory and Mailboxes.

The following firmware names are used by default for these cores, and
can be overridden in a board dts file if needed:
    am65x-mcu-r5f0_0-fw (LockStep mode and for Core0 in Split mode)
    am65x-mcu-r5f0_1-fw (Core1 in Split mode)

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20201029033802.15366-2-s-anna@ti.com