dts: bindings: add binding for bluetooth modules

Provide dts yaml bindings for bluetooth modules
used by 96b_carbon and disco_l475_iot1 boards.

Devices are denoted as spi-devices and inherit from
spi-device.yaml

Signed-off-by: Yannis Damigos <giannis.damigos@gmail.com>
diff --git a/dts/bindings/bluetooth/st,spbtle-rf.yaml b/dts/bindings/bluetooth/st,spbtle-rf.yaml
new file mode 100644
index 0000000..137747a
--- /dev/null
+++ b/dts/bindings/bluetooth/st,spbtle-rf.yaml
@@ -0,0 +1,21 @@
+#
+# Copyright (c) 2018, I-SENSE group of ICCS
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+title: STMicroelectronics SPBTLE-RF bluetooth module
+id: st,spbtle-rf
+version: 0.1
+
+description: >
+    This binding gives the base representation of SPBTLE-RF bluetooth module
+
+inherits:
+    !include spi-device.yaml
+
+properties:
+    compatible:
+      constraint: "st,spbtle-rf"
+
+...
diff --git a/dts/bindings/bluetooth/zephyr,bt-hci-spi.yaml b/dts/bindings/bluetooth/zephyr,bt-hci-spi.yaml
new file mode 100644
index 0000000..1cd2d87
--- /dev/null
+++ b/dts/bindings/bluetooth/zephyr,bt-hci-spi.yaml
@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2018, I-SENSE group of ICCS
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+title: Bluetooth module based on Zephyr's Bluetooth HCI SPI driver
+id: zephyr,bt-hci-spi
+version: 0.1
+
+description: >
+    This binding gives the base representation of a bluetooth module which use
+    Zephyr's bluetooth Host Controller Interface SPI driver (e.g. nRF51822).
+
+inherits:
+    !include spi-device.yaml
+
+properties:
+    compatible:
+      constraint: "zephyr,bt-hci-spi"
+
+...