docs: cgroup-v1: Clarify that domain levels are system-specific

Add a clarification that domain levels are system-specific
and where to check for system details.

Signed-off-by: Vitalii Bursov <vitaly@bursov.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/42b177a2e897cdf880caf9c2025f5b609e820334.1714488502.git.vitaly@bursov.com

Author: vitalyvb

Documentation/admin-guide/cgroup-v1/cpusets.rst

@@ -568,7 +568,7 @@ on the next tick.  For some applications in special situation, waiting
 
 The 'cpuset.sched_relax_domain_level' file allows you to request changing
 this searching range as you like.  This file takes int value which
-indicates size of searching range in levels ideally as follows,
+indicates size of searching range in levels approximately as follows,
 otherwise initial value -1 that indicates the cpuset has no request.
 
 ====== ===========================================================
@@ -581,6 +581,11 @@ otherwise initial value -1 that indicates the cpuset has no request.
    5   search system wide [on NUMA system]
 ====== ===========================================================
 
+Not all levels can be present and values can change depending on the
+system architecture and kernel configuration. Check
+/sys/kernel/debug/sched/domains/cpu*/domain*/ for system-specific
+details.
+
 The system default is architecture dependent.  The system default
 can be changed using the relax_domain_level= boot parameter.