dt-bindings: memory: Document Tegra210 EMC table

Add device tree bindings for the Tegra210 EMC table that is passed via a
reserved-memory device tree node.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211217165919.2700920-1-thierry.reding@gmail.com

Documentation/devicetree/bindings/reserved-memory/nvidia,tegra210-emc-table.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/reserved-memory/nvidia,tegra210-emc-table.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVIDIA Tegra210 EMC Frequency Table Device Tree Bindings
+
+maintainers:
+  - Thierry Reding <thierry.reding@gmail.com>
+  - Jon Hunter <jonathanh@nvidia.com>
+
+description: On Tegra210, firmware passes a binary representation of the
+  EMC frequency table via a reserved memory region.
+
+allOf:
+  - $ref: "reserved-memory.yaml"
+
+properties:
+  compatible:
+    const: nvidia,tegra210-emc-table
+
+  reg:
+    description: region of memory reserved by firmware to pass the EMC
+      frequency table
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg