doc: update the documentation according to "iasl" refinement

This patch updates the documentation according to the refinement on
the detection and the version verification of "iasl".

Tracked-On: #7880

Signed-off-by: Shiqing Gao <shiqing.gao@intel.com>

doc/reference/hv-make-options.rst

@@ -34,8 +34,8 @@ The following table shows ACRN-specific command-line options:
        is ``n``.)
 
    * - ``ASL_COMPILER``
-     - Optional. Use an ``iasl`` compiler that is not in the default path
-       (``/usr/sbin``).
+     - Optional. Specify the path to the ``iasl`` compiler on the development machine.
+       (If not provided, the default value is derived from ``which iasl``.)
 
    * - ``O``
      - Optional. Path to the directory where the built files will be stored.

doc/user-guides/acrn-dm-parameters.rst

@@ -325,6 +325,21 @@ Here are descriptions for each of these ``acrn-dm`` command line parameters:
 
       --ssram
 
+----
+
+``--iasl <iasl_compiler_path>``
+   Specify the path to ``iasl`` compiler on the target machine.
+
+   If ``--iasl <iasl_compiler_path>`` is specified as the ``acrn-dm`` parameter,
+   acrn-dm uses <iasl_compiler_path> as the path to the ``iasl`` compiler;
+   otherwise, ``which iasl`` is used to detect where the ``iasl`` compiler is located.
+
+   usage::
+
+      --iasl /usr/local/bin/iasl
+
+   uses ``/usr/local/bin/iasl`` as the path to the ``iasl`` compiler
+
 .. _emul_config:
 
 Emulated PCI Device Types