serdev: Split and export serdev_acpi_get_uart_resource()

The same as for I²C Serial Bus resource split and export
serdev_acpi_get_uart_resource(). We have already a few users
one of which is converted here.

Rationale of this is to consolidate parsing UART Serial Bus
resource in one place as it's done, e.g., for I²C Serial Bus.

Reviewed-by: Hans de Goede <[e-mail]>
Acked-by: Hans de Goede <[e-mail]>
Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serdev/core.c

···
 	int index;
 };
 
+/**
+ * serdev_acpi_get_uart_resource - Gets UARTSerialBus resource if type matches
+ * @ares:	ACPI resource
+ * @uart:	Pointer to UARTSerialBus resource will be returned here
+ *
+ * Checks if the given ACPI resource is of type UARTSerialBus.
+ * In this case, returns a pointer to it to the caller.
+ *
+ * Return: True if resource type is of UARTSerialBus, otherwise false.
+ */
+bool serdev_acpi_get_uart_resource(struct acpi_resource *ares,
+				   struct acpi_resource_uart_serialbus **uart)
+{
+	struct acpi_resource_uart_serialbus *sb;
+
+	if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
+		return false;
+
+	sb = &ares->data.uart_serial_bus;
+	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_UART)
+		return false;
+
+	*uart = sb;
+	return true;
+}
+EXPORT_SYMBOL_GPL(serdev_acpi_get_uart_resource);
+
 static int acpi_serdev_parse_resource(struct acpi_resource *ares, void *data)
 {
 	struct acpi_serdev_lookup *lookup = data;
 	struct acpi_resource_uart_serialbus *sb;
 	acpi_status status;
 
-	if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
-		return 1;
-
-	if (ares->data.common_serial_bus.type != ACPI_RESOURCE_SERIAL_TYPE_UART)
+	if (!serdev_acpi_get_uart_resource(ares, &sb))
 		return 1;
 
 	if (lookup->index != -1 && lookup->n++ != lookup->index)
 		return 1;
-
-	sb = &ares->data.uart_serial_bus;
 
 	status = acpi_get_handle(lookup->device_handle,
 				 sb->resource_source.string_ptr,
···
 		return 1;
 
 	/*
-	 * NOTE: Ideally, we would also want to retreive other properties here,
+	 * NOTE: Ideally, we would also want to retrieve other properties here,
 	 * once setting them before opening the device is supported by serdev.
 	 */
 

include/linux/serdev.h

···
 }
 #endif /* CONFIG_SERIAL_DEV_CTRL_TTYPORT */
 
+struct acpi_resource;
+struct acpi_resource_uart_serialbus;
+
+#ifdef CONFIG_ACPI
+bool serdev_acpi_get_uart_resource(struct acpi_resource *ares,
+				   struct acpi_resource_uart_serialbus **uart);
+#else
+static inline bool serdev_acpi_get_uart_resource(struct acpi_resource *ares,
+						 struct acpi_resource_uart_serialbus **uart)
+{
+	return false;
+}
+#endif /* CONFIG_ACPI */
+
 #endif /*_LINUX_SERDEV_H */