driver core: platform: Document return type of more functions

I can't always remember the return values of these functions, and so I
usually jump to the function to read the kernel-doc and see that it
doesn't tell me. Then I have to spend more time reading the code to jump
to the function that actually tells me the return values. Let's document
it here so that we don't all have to spend time digging through the code
to understand the return values.

Cc: <linux-doc@vger.kernel.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20200910060440.2302925-1-swboyd@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/platform.c

@@ -45,6 +45,8 @@ EXPORT_SYMBOL_GPL(platform_bus);
  * @dev: platform device
  * @type: resource type
  * @num: resource index
+ *
+ * Return: a pointer to the resource or NULL on failure.
  */
 struct resource *platform_get_resource(struct platform_device *dev,
 				       unsigned int type, unsigned int num)
@@ -70,6 +72,9 @@ EXPORT_SYMBOL_GPL(platform_get_resource);
  *        resource management
  * @index: resource index
  * @res: optional output parameter to store a pointer to the obtained resource.
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
  */
 void __iomem *
 devm_platform_get_and_ioremap_resource(struct platform_device *pdev,
@@ -91,6 +96,9 @@ EXPORT_SYMBOL_GPL(devm_platform_get_and_ioremap_resource);
  * @pdev: platform device to use both for memory resource lookup as well as
  *        resource management
  * @index: resource index
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
  */
 void __iomem *devm_platform_ioremap_resource(struct platform_device *pdev,
 					     unsigned int index)
@@ -106,6 +114,9 @@ EXPORT_SYMBOL_GPL(devm_platform_ioremap_resource);
  * @pdev: platform device to use both for memory resource lookup as well as
  *        resource management
  * @index: resource index
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
  */
 void __iomem *devm_platform_ioremap_resource_wc(struct platform_device *pdev,
 						unsigned int index)
@@ -124,6 +135,9 @@ void __iomem *devm_platform_ioremap_resource_wc(struct platform_device *pdev,
  * @pdev: platform device to use both for memory resource lookup as well as
  *	  resource management
  * @name: name of the resource
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
  */
 void __iomem *
 devm_platform_ioremap_resource_byname(struct platform_device *pdev,