Documentation/gpu: Reference articles on Linux graphics stack

Add two articles on LWN about the Linux graphics stack to DRM's
list of external references. The articles document the graphics
output as a whole, including the kernel side.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240115113908.25897-1-tzimmermann@suse.de

Documentation/gpu/introduction.rst

@@ -164,6 +164,8 @@ Conference talks
 Slides and articles
 -------------------
 
+* `The Linux graphics stack in a nutshell, part 1 <https://lwn.net/Articles/955376/>`_ - Thomas Zimmermann (2023)
+* `The Linux graphics stack in a nutshell, part 2 <https://lwn.net/Articles/955708/>`_ - Thomas Zimmermann (2023)
 * `Understanding the Linux Graphics Stack <https://bootlin.com/doc/training/graphics/graphics-slides.pdf>`_ - Bootlin (2022)
 * `DRM KMS overview <https://wiki.st.com/stm32mpu/wiki/DRM_KMS_overview>`_ - STMicroelectronics (2021)
 * `Linux graphic stack <https://studiopixl.com/2017-05-13/linux-graphic-stack-an-overview>`_ - Nathan Gauër (2017)