manpages: virsh: Use disclaimer from 'virNodeGetInfo()' for 'virsh nodeinfo'

Adapt the disclarimer about the data not being accurate in many cases
from the API docs to the virsh command using the aforementioned API.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

docs/manpages/virsh.rst

@@ -427,10 +427,25 @@ nodeinfo
    nodeinfo
 
 Returns basic information about the node, like number and type of CPU,
-and size of the physical memory. The output corresponds to virNodeInfo
-structure. Specifically, the "CPU socket(s)" field means number of CPU
-sockets per NUMA cell. The information libvirt displays is dependent
-upon what each architecture may provide.
+and size of the physical memory.
+
+Use of this command is strongly discouraged as the information provided
+is not guaranteed to be accurate on all hardware platforms.
+
+The *CPU frequency* value merely reflects the speed that the first CPU in the
+machine is currently running at. This speed may vary across CPUs and changes
+continually as the host OS throttles.
+
+The data structure used to fetch the data is not extensible thus only supports
+global nodes/sockets/cores/threads (sockets/cores/threads is per NUMA node)
+topology information. If the host CPU has any further groupings (e.g.
+dies, clusters, etc) or the NUMA topology is non-symmetrical the data structure
+can't faithfully represent the system. In such cases a fake topology
+(nodes = 1, sockets = 1, cores = number of host cpus, threads = 1) which
+only correctly represents the total host CPU count is reported.
+
+Recommended replacement is to use the *capabilities* command which reports
+the data (except frequency) under ``/capabilities/host/topology`` XPath.
 
 
 nodecpumap