Add the serdev (UART) transport for the Realtek PSE MCU core. It registers
the MCU as a serdev device and provides the send/recv callbacks the core
uses to exchange the 12-byte frames, receiving asynchronously via the
serdev receive_buf callback.

The baud rate defaults to 19200 and can be overridden per board with the
"current-speed" property.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20260813222036.873930-5-jelonek.jonas@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Add the I2C/SMBus transport for the Realtek PSE MCU core. It registers
the MCU on an I2C bus and provides the send/recv callbacks the core
uses to exchange the 12-byte frames.

The MCU firmware expects one of two framings on the I2C bus, and which one
is part of the compatible: '-smbus' (reads carry a leading command byte
and a repeated start) or raw '-i2c' (bare block writes and reads). The
match data flags the raw-I2C case; SMBus is the default because that's
what the majority of devices uses.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20260813222036.873930-4-jelonek.jonas@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

A range of managed Realtek-based PoE switches use a small microcontroller
on the PCB to front the actual PSE silicon. The host CPU talks to that
MCU over I2C/SMBus or UART using a fixed 12-byte request/response
protocol with a trailing checksum; the PSE chips are managed by the MCU
and are not accessed directly. Two generations of the protocol exist -
both Realtek's - diverging in opcode numbering and a few response
layouts; the driver handles this with a per-dialect opcode table and
parser hooks for the responses that differ, selected by the compatible.
The specific PSE chip behind the MCU is detected at runtime and only
influences per-chip constants (power scaling and the per-port cap).

This core module implements the protocol, message framing, the dialect
machinery and the pse_controller_ops glue, and exports a registration
helper for transport modules. The I2C and UART transports that drive it
follow in the next patches; the core (PSE_REALTEK_MCU) is selected
automatically by those transports and is not user-selectable on its own.

The realtek-pse-mcu-* files and PSE_REALTEK_MCU* symbols match the
realtek,pse-mcu-* compatibles (see the binding for the naming rationale).
The two protocol generations - gen1 on older Broadcom-PSE boards, gen2 on
Realtek's own PSE silicon - are both Realtek's, handled by the same shared
core, each selecting its dialect via the compatible.

Power budgeting is left to the MCU firmware; the driver advertises
PSE_BUDGET_EVAL_STRAT_DYNAMIC accordingly.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Link: https://patch.msgid.link/20260813222036.873930-3-jelonek.jonas@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Add a driver for the Skyworks Si3474 I2C Power Sourcing Equipment
controller.

Driver supports basic features of Si3474 IC:
- get port status,
- get port power,
- get port voltage,
- enable/disable port power.

Only 4p configurations are supported at this moment.

Signed-off-by: Piotr Kubik <piotr.kubik@adtran.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/9b72c8cd-c8d3-4053-9c80-671b9481d166@adtran.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Add a new driver for the TI TPS23881 I2C Power Sourcing Equipment
controller.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://lore.kernel.org/r/20240417-feature_poe-v9-14-242293fd1900@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add a new driver for the PD692x0 I2C Power Sourcing Equipment controller.
This driver only support i2c communication for now.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240417-feature_poe-v9-12-242293fd1900@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Add generic, regulator based PSE driver to support simple Power Sourcing
Equipment without automatic classification support.

This driver was tested on 10Bast-T1L switch with regulator based PoDL PSE.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

This framework was create with intention to provide support for Ethernet PSE
(Power Sourcing Equipment) and PDs (Powered Device).

At current step this patch implements generic PSE support for PoDL (Power over
Data Lines 802.3bu) specification with reserving name space for PD devices as
well.

This framework can be extended to support 802.3af and 802.3at "Power via the
Media Dependent Interface" (or PoE/Power over Ethernet)

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>