mfd: core: Preserve OF node when ACPI handle is present

Switch device_set_node to set_primary_fwnode, so that the ACPI fwnode
does not overwrite the of_node with NULL.

This allows MFD children with both OF nodes and ACPI handles to have OF
nodes again.

Cc: stable@vger.kernel.org
Fixes: 51e3b25 ("mfd: core: Make use of device_set_node()")
Signed-off-by: Brian Mak <makb@juniper.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260325223024.35992-1-makb@juniper.net
Signed-off-by: Lee Jones <lee@kernel.org>

Author: makb-juniper

drivers/mfd/mfd-core.c

@@ -88,7 +88,17 @@ static void mfd_acpi_add_device(const struct mfd_cell *cell,
 		}
 	}
 
-	device_set_node(&pdev->dev, acpi_fwnode_handle(adev ?: parent));
+	/*
+	 * NOTE: The fwnode design doesn't allow proper stacking/sharing. This
+	 * should eventually turn into a device fwnode API call that will allow
+	 * prepending to a list of fwnodes (with ACPI taking precedence).
+	 *
+	 * set_primary_fwnode() is used here, instead of device_set_node(), as
+	 * device_set_node() will overwrite the existing fwnode, which may be an
+	 * OF node that was populated earlier. To support a use case where ACPI
+	 * and OF is used in conjunction, we call set_primary_fwnode() instead.
+	 */
+	set_primary_fwnode(&pdev->dev, acpi_fwnode_handle(adev ?: parent));
 }
 #else
 static inline void mfd_acpi_add_device(const struct mfd_cell *cell,