Documentation/osnoise: Add osnoise/options documentation

Add the documentation about the osnoise/options file, the options,
and some additional explanation about the OSNOISE_WORKLOAD option.

Link: https://lkml.kernel.org/r/fde5567a4bae364f67fd1e9a644d1d62862618a6.1670623111.git.bristot@kernel.org

Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: Daniel Bristot de Oliveira

Documentation/trace/osnoise-tracer.rst

@@ -92,8 +92,8 @@ Note that the example above shows a high number of HW noise samples.
 The reason being is that this sample was taken on a virtual machine,
 and the host interference is detected as a hardware interference.
 
-Tracer options
----------------------
+Tracer Configuration
+--------------------
 
 The tracer has a set of options inside the osnoise directory, they are:
 
@@ -115,6 +115,22 @@ The tracer has a set of options inside the osnoise directory, they are:
    NO_OSNOISE_WORKLOAD disables the OSNOISE_WORKLOAD option. The
    special DEAFAULTS option resets all options to the default value.
 
+Tracer Options
+--------------
+
+The osnoise/options file exposes a set of on/off configuration options for
+the osnoise tracer. These options are:
+
+ - DEFAULTS: reset the options to the default value.
+ - OSNOISE_WORKLOAD: do not dispatch osnoise workload (see dedicated
+   section below).
+ - PANIC_ON_STOP: call panic() if the tracer stops. This option serves to
+   capture a vmcore.
+ - OSNOISE_PREEMPT_DISABLE: disable preemption while running the osnoise
+   workload, allowing only IRQ and hardware-related noise.
+ - OSNOISE_IRQ_DISABLE: disable IRQs while running the osnoise workload,
+   allowing only NMIs and hardware-related noise, like hwlat tracer.
+
 Additional Tracing
 ------------------