Always set encoding to UTF-8 for OSM data

docs/source/known_issues.md

@@ -102,7 +102,8 @@ df = read_dataframe(path, INTERLEAVED_READING=True)
 
 We recommend the following to sidestep performance issues:
 
--   always download remote OSM data sources to local files before attempting
+-   download remote OSM data sources to local files before attempting
     to read
+-   the `use_arrow=True` option may speed up reading from OSM files
 -   if possible, use a different tool such as `ogr2ogr` to translate the OSM
     data source into a more performant format for reading by layer, such as GPKG

pyogrio/_io.pyx

@@ -438,13 +438,19 @@ cdef detect_encoding(OGRDataSourceH ogr_dataset, OGRLayerH ogr_layer):
     -------
     str or None
     """
+
     if OGR_L_TestCapability(ogr_layer, OLCStringsAsUTF8):
         return 'UTF-8'
 
     driver = get_driver(ogr_dataset)
     if driver == 'ESRI Shapefile':
         return 'ISO-8859-1'
 
+    if driver == "OSM":
+        # always set OSM data to UTF-8
+        # per https://help.openstreetmap.org/questions/2172/what-encoding-does-openstreetmap-use
+        return "UTF-8"
+
     return None