This syscon child node represents a single SoC device controlled by the
PMGR block. This layout allows us to declare all device power state
controls (power/clock gating and reset) in the device tree, including
dependencies, instead of hardcoding it into the driver. The register
layout is uniform.

Each pmgr-pwrstate node provides genpd and reset features, to be
consumed by downstream device nodes.

Future SoCs are expected to use backwards compatible registers, and the
"apple,pmgr-pwrstate" represents any such interfaces (possibly with
additional features gated by the more specific compatible), allowing
them to be bound without driver updates. If a backwards incompatible
change is introduced in future SoCs, it will require a new compatible,
such as "apple,pmgr-pwrstate-v2".

Signed-off-by: Hector Martin <redacted>
---
 .../bindings/power/apple,pmgr-pwrstate.yaml   | 117 ++++++++++++++++++
 MAINTAINERS                                   |   1 +
 2 files changed, 118 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml

diff --git a/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml b/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml
new file mode 100644
index 000000000000..a14bf5f30ff0
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml

@@ -0,0 +1,117 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/apple,pmgr-pwrstate.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple SoC PMGR Power States
+
+maintainers:
+  - Hector Martin <marcan@marcan.st>
+
+allOf:
+  - $ref: "power-domain.yaml#"
+
+description: |
+  Apple SoCs include a PMGR block responsible for power management,
+  which can control various clocks, resets, power states, and
+  performance features. This binding describes the device power
+  state registers, which control power states and resets.
+
+  Each instance of a power controller within the PMGR syscon node
+  represents a generic power domain provider, as documented in
+  Documentation/devicetree/bindings/power/power-domain.yaml.
+  The provider controls a single SoC block. The power hierarchy is
+  represented via power-domains relationships between these nodes.
+
+  See Documentation/devicetree/bindings/arm/apple/apple,pmgr.yaml
+  for the top-level PMGR node documentation.
+
+  IP cores belonging to a power domain should contain a
+  "power-domains" property that is a phandle for the
+  power domain node representing the domain.