Doc/nb/intel/haswell: Add a list of known issues

Change-Id: If0339831550f6c70e8056f78633e9a402f35a793
Signed-off-by: Tristan Corrick <tristan@corrick.kiwi>
Reviewed-on: https://review.coreboot.org/c/30455
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

Documentation/mainboard/asrock/h81m-hds.md

@@ -78,6 +78,10 @@ facing towards the bottom of the board.
   in coreboot. The `coretemp` driver can still be used for accurate CPU
   temperature readings from an OS.
 
+```eval_rst
+Please also see :doc:`../../northbridge/intel/haswell/known-issues`.
+```
+
 ## Untested
 
 - parallel port

Documentation/northbridge/intel/haswell/index.md

@@ -6,3 +6,7 @@ coreboot.
 ## Proprietary blobs
 
 - [mrc.bin](mrc.bin.md)
+
+## Issues
+
+- [Known issues](known-issues.md)

Documentation/northbridge/intel/haswell/known-issues.md

@@ -0,0 +1,28 @@
+# Known issues with Haswell
+
+These issues are specific to the Haswell architecture. For a given
+mainboard, there might be additional issues to those listed here.
+
+## PCIe graphics
+
+```eval_rst
+Using a PCIe graphics card for display output is not currently
+supported. This is because :doc:`./mrc.bin` requires workarounds to
+have such a feature working correctly.
+```
+
+However, there is a [patch on Gerrit][hsw-gfx-gerrit] that allows PCIe
+graphics to be used for display output. This patch is not guaranteed to
+be of the same level of quality as code committed to coreboot.
+
+Still, in some cases, a PCIe graphics card can be used for rendering,
+while the integrated graphics device is used for display output. This
+can be achieved under GNU/Linux by using [PRIME GPU offloading][PRIME].
+
+## PCIe 3.0
+
+Only PCIe 2.0 has been tested so far. PCIe 3.0 could potentially have
+stability issues.
+
+[PRIME]: https://wiki.archlinux.org/index.php/PRIME
+[hsw-gfx-gerrit]: https://review.coreboot.org/c/30456