dts: bindings: add support for the flash driver name

So far, DT did not support the flash driver name.
Any flash-controller should have the appropriate
flash driver that should be identified by its name.

This path adds generic support for extract the description
from the flash-controller node,
adds implementation of this property for all nrf5x targets.


Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

dts/bindings/flash_controller/flash-controller.yaml

@@ -0,0 +1,34 @@
+---
+title: flash controller Base Structure
+id: soc-nv-flash-controller
+version: 0.1
+
+description: >
+    This binding gives the base structures for all flash controller devices
+
+properties:
+    label:
+      type: string
+      category: required
+      description: Human readable string describing the device (used by Zephyr for API name)
+      generation: define
+
+    reg:
+      type: array
+      description: mmio register space
+      generation: define
+      category: required
+
+    interrupts:
+      type: array
+      category: optional
+      description: required interrupts
+      generation: define
+
+    interrupt-names:
+      type: stringlist
+      category: optional
+      description: names of required interrupts
+      generation: define
+
+...

dts/bindings/flash_controller/nordic,nrf51-flash-controller.yaml

@@ -0,0 +1,19 @@
+---
+title: Nordic NVMC
+id: nordic,nrf51-flash-controller
+version: 0.1
+
+description: >
+    This binding gives a base representation of the Nordic NVMC
+
+inherits:
+    !include flash-controller.yaml
+
+properties:
+    compatible:
+      type: string
+      category: required
+      description: compatible strings
+      constraint: "nrf,nrf51-flash-controller"
+
+...

dts/bindings/flash_controller/nordic,nrf52-flash-controller.yaml

@@ -0,0 +1,19 @@
+---
+title: Nordic NVMC
+id: nordic,nrf52-flash-controller
+version: 0.1
+
+description: >
+    This binding gives a base representation of the Nordic NVMC
+
+inherits:
+    !include flash-controller.yaml
+
+properties:
+    compatible:
+      type: string
+      category: required
+      description: compatible strings
+      constraint: "nrf,nrf52-flash-controller"
+
+...