DOC: Clarify read_raw_nirx expects directory path, not file path (mne-tools#13541)

Author: natinew77-creator

mne/io/nirx/nirx.py

@@ -41,7 +41,10 @@ def read_raw_nirx(
     Parameters
     ----------
     fname : path-like
-        Path to the NIRX data folder or header file.
+        Path to the NIRX data folder (directory containing NIRX files) or
+        the ``.hdr`` header file within that folder. The function will
+        automatically find and read all required NIRX files from the
+        directory.
     %(saturated)s
     %(preload)s
     %(encoding_nirx)s

mne/utils/docs.py

@@ -2884,6 +2884,11 @@ def _reflow_param_docstring(docstring, has_first_line=True, width=75):
 called .nosatflags_wlX. As NaN values can cause unexpected behaviour with
 mathematical functions the default behaviour is to return the
 saturated data.
+
+.. note::
+    This function expects ``fname`` to be a path to a directory containing the
+    NIRX data files (e.g., ``.hdr``, ``.wl1``, ``.wl2``, etc.). If you have a
+    ``.snirf`` file, use :func:`mne.io.read_raw_snirf` instead.
 """
 
 docdict["niter"] = """