refactor(dbus): Move D-Bus helper functions to a dedicated file

Consolidated `REVPI_DBUS_*` constants and `extend_interface` function
into `dbus_helper.py` for better modularity and reusability. Updated
imports across modules to reflect this change.

src/revpi_middleware/dbus_middleware1/dbus_helper.py

@@ -0,0 +1,126 @@
+# -*- coding: utf-8 -*-
+# SPDX-FileCopyrightText: 2020-2023 Sven Sager
+# SPDX-License-Identifier: GPL-2.0-or-later
+"""
+Helper for the process image.
+
+The ResetDriverWatchdog class is a copy of revpipyload project module "watchdogs"
+https://github.com/naruxde/revpipyload/blob/b51c2b617a57cc7d96fd67e1da9f090a0624eacb/src/revpipyload/watchdogs.py
+"""
+
+import os
+from fcntl import ioctl
+from logging import getLogger
+from threading import Thread
+
+log = getLogger(__name__)
+
+REVPI_DBUS_NAME = "com.revolutionpi.middleware1"
+REVPI_DBUS_BASE_PATH = "/com/revolutionpi/middleware1"
+
+
+class ResetDriverWatchdog(Thread):
+    """Watchdog to catch the reset_driver action."""
+
+    def __init__(self, pi_control_device="/dev/piControl0"):
+        super(ResetDriverWatchdog, self).__init__()
+        self.procimg = pi_control_device
+        self.daemon = True
+        self._calls = []
+        self._exit = False
+        self._fh = None
+        self.not_implemented = False
+        """True, if KB_WAIT_FOR_EVENT is not implemented in piControl."""
+        self._triggered = False
+        self.start()
+
+    def run(self):
+        """
+        Mainloop of watchdog for reset_driver.
+
+        If the thread can not open the process image or the IOCTL is not
+        implemented (wheezy), the thread function will stop. The trigger
+        property will always return True.
+        """
+        log.debug("enter ResetDriverWatchdog.run()")
+
+        try:
+            self._fh = os.open(self.procimg, os.O_RDONLY)
+        except Exception:
+            self.not_implemented = True
+            log.error(
+                "can not open process image at '{0}' for reset_driver watchdog"
+                "".format(self.procimg)
+            )
+            return
+
+        # The ioctl will return 2 byte (c-type int)
+        byte_buff = bytearray(2)
+        while not self._exit:
+            try:
+                rc = ioctl(self._fh, 19250, byte_buff)
+                if rc == 0 and byte_buff[0] == 1:
+                    self._triggered = True
+                    log.debug("reset_driver detected")
+                    for func in self._calls:
+                        func()
+            except Exception:
+                self.not_implemented = True
+                os.close(self._fh)
+                self._fh = None
+                log.warning("IOCTL KB_WAIT_FOR_EVENT is not implemented")
+                return
+
+        log.debug("leave ResetDriverWatchdog.run()")
+
+    def register_call(self, function):
+        """Register a function, if watchdog triggers."""
+        if not callable(function):
+            return ValueError("Function is not callable.")
+        if function not in self._calls:
+            self._calls.append(function)
+
+    def stop(self):
+        """Stop watchdog for reset_driver."""
+        log.debug("enter ResetDriverWatchdog.stop()")
+
+        self._exit = True
+        if self._fh is not None:
+            os.close(self._fh)
+            self._fh = None
+
+        log.debug("leave ResetDriverWatchdog.stop()")
+
+    def unregister_call(self, function=None):
+        """Remove a function call on watchdog trigger."""
+        if function is None:
+            self._calls.clear()
+        elif function in self._calls:
+            self._calls.remove(function)
+
+    @property
+    def triggered(self):
+        """Will return True one time after watchdog was triggered."""
+        rc = self._triggered
+        self._triggered = False
+        return rc
+
+
+def extend_interface(*args) -> str:
+    """
+    Extends an interface name by appending additional segments to a pre-defined base name.
+
+    This function takes multiple arguments, concatenates them with a predefined base
+    interface name, and returns the resulting string, effectively constructing an
+    extended interface name.
+
+    Args:
+        *args: str
+            Components to be appended to the base interface name.
+
+    Returns:
+        str
+            Fully constructed interface name by joining the base interface name with
+            the provided segments.
+    """
+    return ".".join([REVPI_DBUS_NAME, *args])