dt-bindings: mailbox: arm,mhu: Make secure interrupt optional

The secure interrupt is only useful to secure world, therefore for NS
users it shouldn't be required. Make it optional.

This fixes a warning on Arm Juno board:

mhu@2b1f0000: interrupts: [[0, 36, 4], [0, 35, 4]] is too short

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20220728190810.1290857-1-robh@kernel.org

dt-bindings: mailbox : arm,mhu: Use examples with matching schema

Currently the example provided in arm,mhu schema complains as below:

Documentation/devicetree/bindings/mailbox/arm,mhu.example.dt.yaml :0:0:
/example-0/soc/scb@2e000000: failed to match any schema with compatible:
['fujitsu,mb86s70-scb-1.0']

Fix the same using examples based on Juno platform. The old SCPI firmware
used MHU with standard 32-bit data transfer protocol while the new SCMI
firmware uses MHU and expects to be used in doorbell mode. Update example
with SCPI and SCMI firmware nodes to demonstrate both 32-bit data transfer
and doorbell mode of MHU operations

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20210604205710.1944363-6-sudeep.holla@arm.com
Signed-off-by: Rob Herring <robh@kernel.org>

dt-bindings: mailbox : arm,mhu: Fix arm,scpi example used here

Once the arm,scpi binding is converted to YAML format, the following
errors will be seen when doing `make DT_CHECKER_FLAGS=-m dt_binding_check`

From schema: Documentation/devicetree/bindings/firmware/arm,scpi.yaml
Documentation/devicetree/bindings/mailbox/arm,mhu.example.dt.yaml:
scpi@2f000000: $nodename:0: 'scpi' was expected
Documentation/devicetree/bindings/mailbox/arm,mhu.example.dt.yaml:
scpi@2f000000: reg: [[0, 788529152, 0, 512]] is not of type 'object'
Documentation/devicetree/bindings/mailbox/arm,mhu.example.dt.yaml:
scpi@2f000000: 'shmem' is a required property

Fix those error following the SCPI bindings.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20210604205710.1944363-2-sudeep.holla@arm.com
Signed-off-by: Rob Herring <robh@kernel.org>

dt-bindings: Drop redundant maxItems/items

'maxItems' equal to the 'items' list length is redundant. 'maxItems' is
preferred for a single entry while greater than 1 should have an 'items'
list.

A meta-schema check for this is pending once these existing cases are
fixed.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: dri-devel@lists.freedesktop.org
Cc: dmaengine@vger.kernel.org
Cc: alsa-devel@alsa-project.org
Cc: linux-usb@vger.kernel.org
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20201222040645.1323611-1-robh@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

dt-bindings: mailbox: add doorbell support to ARM MHU

The ARM MHU's reference manual states following:

"The MHU drives the signal using a 32-bit register, with all 32 bits
logically ORed together. The MHU provides a set of registers to enable
software to set, clear, and check the status of each of the bits of this
register independently. The use of 32 bits for each interrupt line
enables software to provide more information about the source of the
interrupt. For example, each bit of the register can be associated with
a type of event that can contribute to raising the interrupt."

This patch thus extends the MHU controller's DT binding to add support
for doorbell mode.

Though the same MHU hardware controller is used in the two modes, A new
compatible string is added here to represent the combination of the MHU
hardware and the firmware sitting on the other side (which expects each
bit to represent a different signal now).

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Co-developed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

dt-bindings: mailbox : arm,mhu: Convert to Json-schema

Convert the DT binding over to Json-schema.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>