device property: Implement device_is_big_endian()

Some users want to use the struct device pointer to see if the
device is big endian in terms of Open Firmware specifications,
i.e. if it has a "big-endian" property, or if the kernel was
compiled for BE *and* the device has a "native-endian" property.

Provide inline helper for the users.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20231025184259.250588-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: andy-shev

include/linux/property.h

@@ -80,12 +80,38 @@ int fwnode_property_match_string(const struct fwnode_handle *fwnode,
 
 bool fwnode_device_is_available(const struct fwnode_handle *fwnode);
 
+static inline bool fwnode_device_is_big_endian(const struct fwnode_handle *fwnode)
+{
+	if (fwnode_property_present(fwnode, "big-endian"))
+		return true;
+	if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) &&
+	    fwnode_property_present(fwnode, "native-endian"))
+		return true;
+	return false;
+}
+
 static inline
 bool fwnode_device_is_compatible(const struct fwnode_handle *fwnode, const char *compat)
 {
 	return fwnode_property_match_string(fwnode, "compatible", compat) >= 0;
 }
 
+/**
+ * device_is_big_endian - check if a device has BE registers
+ * @dev: Pointer to the struct device
+ *
+ * Returns: true if the device has a "big-endian" property, or if the kernel
+ * was compiled for BE *and* the device has a "native-endian" property.
+ * Returns false otherwise.
+ *
+ * Callers would nominally use ioread32be/iowrite32be if
+ * device_is_big_endian() == true, or readl/writel otherwise.
+ */
+static inline bool device_is_big_endian(const struct device *dev)
+{
+	return fwnode_device_is_big_endian(dev_fwnode(dev));
+}
+
 /**
  * device_is_compatible - match 'compatible' property of the device with a given string
  * @dev: Pointer to the struct device