Documentation/soc/amd: Add Family 17h

Begin a directory for AMD soc devices and add an explanation of
how Family 17h works.  Newer AMD systems use a unique paradign
for initializing the x86 processors.

Change-Id: I7bd8649996add80747f6a60b9dfd35a94a560be1
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33399
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

Documentation/soc/amd/index.md

@@ -0,0 +1,8 @@
+# AMD SOC-specific documentation
+
+This section contains documentation about coreboot on specific AMD SOCs.
+
+## Technology
+
+- [Family 17h](family17h.md)
+