dts: Add YAML bindings for Intel SPI driver

Currently found on Galileo board.

Fixes #11064

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>

dts/bindings/spi/intel,intel-spi.yaml

@@ -0,0 +1,32 @@
+#
+# Copyright (c) 2018 Synopsys, Inc. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+title: Intel SPI Controller
+version: 0.1
+
+description: >
+     This is a representation of the Intel SPI controller found on quark x1000.
+
+inherits:
+    !include spi.yaml
+
+properties:
+    compatible:
+      constraint: "intel,intel-spi"
+
+    reg:
+      type: array
+      description: mmio register space
+      generation: define
+      category: required
+
+    interrupts:
+      type: array
+      category: required
+      description: required interrupts
+      generation: define
+
+...