scripts: dts: add special tooling for handling GPIO hog nodes

GPIO hog nodes contain a "gpios" property, but unlike other "*-gpios"
properties, these are not phandle-arrays as they only carry the data part
(e.g. pin, flags) but lack the phandles to the (parent) GPIO controller.

Add special devicetree tooling to handle the "gpios" property of GPIO hog
nodes and generate special devicetree helper macros as if they were phandle
arrays.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>

scripts/dts/python-devicetree/src/devicetree/edtlib.py

@@ -671,6 +671,11 @@ class Node:
       The device's SPI GPIO chip select as a ControllerAndData instance, if it
       exists, and None otherwise. See
       Documentation/devicetree/bindings/spi/spi-controller.yaml in the Linux kernel.
+
+    gpio_hogs:
+      A list of ControllerAndData objects for the GPIOs hogged by the node. The
+      list is empty if the node does not hog any GPIOs. Only relevant for GPIO hog
+      nodes.
     """
     @property
     def name(self):
@@ -837,6 +842,35 @@ class Node:
 
         return parent_cs_lst[cs_index]
 
+    @property
+    def gpio_hogs(self):
+        "See the class docstring"
+
+        if "gpio-hog" not in self.props:
+            return []
+
+        if not self.parent or not "gpio-controller" in self.parent.props:
+            _err(f"GPIO hog {self!r} lacks parent GPIO controller node")
+
+        if not "#gpio-cells" in self.parent._node.props:
+            _err(f"GPIO hog {self!r} parent node lacks #gpio-cells")
+
+        n_cells = self.parent._node.props["#gpio-cells"].to_num()
+        res = []
+
+        for item in _slice(self._node, "gpios", 4*n_cells,
+                           f"4*(<#gpio-cells> (= {n_cells})"):
+            entry = ControllerAndData()
+            entry.node = self
+            entry.controller = self.parent
+            entry.data = self._named_cells(entry.controller, item, "gpio")
+            entry.basename = "gpio"
+            entry.name = None
+
+            res.append(entry)
+
+        return res
+
     def __repr__(self):
         if self.binding_path:
             binding = "binding " + self.binding_path