[PATCH v1 1/8] dt-bindings: mfd: add NXP MC33978/MC34978 MSDI

[Oleksij Rempel]

Add device tree binding documentation for the NXP MC33978 and MC34978
Multiple Switch Detection Interface (MSDI) devices.

These ICs monitor up to 22 mechanical switch contacts in automotive and
industrial environments. They provide configurable wetting currents to
break through contact oxidation and feature extensive hardware protection
against thermal overload and voltage transients (load dumps/brown-outs).

The device interfaces via SPI and is modeled as an MFD due to its discrete
internal functional blocks:
- pinctrl: Manages the 22 switch inputs (SG/SP pins).
- hwmon: Exposes critical hardware faults (OT, OV, UV) and static
  voltage/temperature thresholds.
- mux: Controls the 24-to-1 analog multiplexer to route pin voltages,
  internal temperature, or battery voltage to an external SoC ADC.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
 .../devicetree/bindings/mfd/nxp,mc33978.yaml  | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml

diff --git a/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml b/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
new file mode 100644
index 000000000000..85720f389509
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/nxp,mc33978.yaml
@@ -0,0 +1,86 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/nxp,mc33978.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NXP MC33978/MC34978 Multiple Switch Detection Interface
+
+maintainers:
+  - David Jander <david@xxxxxxxxxxx>
+  - Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
+
+description: |
+  The MC33978 and MC34978 are Multiple Switch Detection Interface (MSDI)
+  devices with 22 switch inputs, integrated fault detection, and analog
+  multiplexer (AMUX) for voltage/temperature monitoring.
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+properties:
+  compatible:
+    enum:
+      - nxp,mc33978
+      - nxp,mc34978
+
+  reg:
+    maxItems: 1
+    description: SPI chip select number
+
+  spi-max-frequency:
+    maximum: 8000000
+    description: Maximum SPI clock frequency (up to 8 MHz)
+
+  interrupts:
+    maxItems: 1
+    description: |
+      INT_B pin interrupt. Active-low, indicates pin state changes or
+      fault conditions.
+
+  interrupt-controller: true
+
+  '#interrupt-cells':
+    const: 2
+    description: |
+      First cell is the IRQ number (0-21 for pins, 22 for faults).
+      Second cell is the trigger type (IRQ_TYPE_* from interrupt-controller.h).
+
+  vddq-supply:
+    description: Digital supply voltage
+
+  vbatp-supply:
+    description: Battery/power supply
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - '#interrupt-cells'
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        msdi: mc33978@0 {
+            compatible = "nxp,mc33978";
+            reg = <0>;
+            spi-max-frequency = <4000000>;
+
+            interrupt-parent = <&gpiog>;
+            interrupts = <9 IRQ_TYPE_LEVEL_LOW>;
+            interrupt-controller;
+            #interrupt-cells = <2>;
+
+            vddq-supply = <&reg_3v3>;
+            vbatp-supply = <&reg_12v>;
+        };
+    };
-- 
2.47.3