At the moment it's not documented that you need to add a bridge before
attaching it. Clarify that.

Suggested-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/all/20250709-sophisticated-loon-of-rain-6ccdd8@houat/
Reviewed-by: Raphael Gallais-Pou <rgallaispou@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/drm_bridge.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 53e7ece36dd940aabd1c0880f296fce7224a12ac..1246a52f8767b52c5f10139aa897824b3c2f28da 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -422,6 +422,9 @@ static bool drm_bridge_is_atomic(struct drm_bridge *bridge)
  * If non-NULL the previous bridge must be already attached by a call to this
  * function.
  *
+ * The bridge to be attached must have been previously added by
+ * drm_bridge_add().
+ *
  * Note that bridges attached to encoders are auto-detached during encoder
  * cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
  * *not* be balanced with a drm_bridge_detach() in driver code.

-- 
2.51.0