Documentation: Begin a RAS section

Add some initial RAS documentation. The expectation is for this to
collect, among others, all the user-visible features for interaction
with the RAS features of the kernel.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231128142049.GTZWX3QQTSaQk/+u53@fat_crate.local

Documentation/RAS/ras.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+Reliability, Availability and Serviceability features
+=====================================================
+
+This documents different aspects of the RAS functionality present in the
+kernel.
+
+Error decoding
+---------------
+
+* x86
+
+Error decoding on AMD systems should be done using the rasdaemon tool:
+https://github.com/mchehab/rasdaemon/
+
+While the daemon is running, it would automatically log and decode
+errors. If not, one can still decode such errors by supplying the
+hardware information from the error::
+
+        $ rasdaemon -p --status <STATUS> --ipid <IPID> --smca
+
+Also, the user can pass particular family and model to decode the error
+string::
+
+        $ rasdaemon -p --status <STATUS> --ipid <IPID> --smca --family <CPU Family> --model <CPU Model> --bank <BANK_NUM>

Documentation/index.rst

@@ -113,6 +113,7 @@ to ReStructured Text format, or are simply too old.
    :maxdepth: 1
 
    staging/index
+   RAS/ras
 
 
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