Add description of decoding error status for vaSyncSurface()

this will indicate APP behavior when meet VA_STATUS_ERROR_DECODING_ERROR from vaSyncSurface

Signed-off-by: Pengxin Yuan <pengxin.yuan@intel.com>

va/va.h

@@ -4187,6 +4187,25 @@ Synchronization
  * This function blocks until all pending operations on the render target
  * have been completed.  Upon return it is safe to use the render target for a
  * different picture.
+ *
+ * Possible errors:
+ * - \ref VA_STATUS_ERROR_INVALID_CONTEXT: This error occurs when the function is provided with an invalid context.
+ *   It is typically due to the context not being properly initialized or already being freed.
+ *   To address this, ensure that the context is correctly initialized and has not been freed.
+ * - \ref VA_STATUS_ERROR_INVALID_SURFACE: This error is triggered when the supplied render target is invalid,
+ *   possibly due to being freed or corrupted. To resolve this, ensure the usage of the correct render target
+ *   and verify its validity and integrity.
+ * - \ref VA_STATUS_ERROR_OPERATION_FAILED: When the attempt to retrieve the status report fails or related work
+ *   on the current surface fails, this error is generated. In such cases, the client can proceed with subsequent
+ *   frames by ignore the error, but it may involve incorrect result like corruption.
+ * - \ref VA_STATUS_ERROR_HW_BUSY: This error indicates that synchronization is still in progress or GPU hang happens.
+ *   The client could call the function again within a period of time to wait hw execution completion.
+ *   If hw execution could not complete successfully, gpu hang and reset may occur, in this case,
+ *   application could try to recover media context by initialing new one.
+ * - \ref VA_STATUS_ERROR_DECODING_ERROR: This error is encountered when macroblock (MB) errors with
+ *   non-conformance input clips are detected during the decoding process. The application can proceed with
+ *   subsequent frames, but it is advised to be aware of potential corruption in the output.
+ *   Call vaQuerySurfaceError could get more details of mb error information.
  */
 VAStatus vaSyncSurface(
     VADisplay dpy,