Add workaround for Radeon R5 (closes: #17789)

wiki/src/support/known_issues/graphics.mdwn

@@ -149,6 +149,22 @@ We need more test results from users: [[!tails_ticket 12482]]
 
 <a id="radeon-r9"></a>
 
+AMD Radeon R5
+-------------
+
+### Affected graphics cards
+
+<table>
+<tr><th>Name</th><th>ID</th><th>Revision number</th></tr>
+<tr><td>Advanced Micro Devices, Inc. [AMD/ATI] Exo UL/ULT/ULP [Radeon R5 M320]</td><td></td><td></td></tr>
+</table>
+
+### Workaround
+
+Adding `radeon.modeset=0 xorg-driver=modesetting` to the
+[[boot options|doc/advanced_topics/boot_options]]
+fixes the issue.
+
 AMD Radeon R9
 -------------