driver core: platform: document registration-failure requirement

Add an explicit comment to document that the reference initialised by
platform_device_register() needs to be released by a call to
platform_device_put() also when registration fails (cf.
device_register()).

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211222104213.5673-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: jhovold

drivers/base/platform.c

@@ -763,6 +763,10 @@ EXPORT_SYMBOL_GPL(platform_device_del);
 /**
  * platform_device_register - add a platform-level device
  * @pdev: platform device we're adding
+ *
+ * NOTE: _Never_ directly free @pdev after calling this function, even if it
+ * returned an error! Always use platform_device_put() to give up the
+ * reference initialised in this function instead.
  */
 int platform_device_register(struct platform_device *pdev)
 {