You can map Revit text fonts to specific DGN text fonts.
On the Text & Fonts tab of the Modify DGN Export Setup dialog (see Export to DGN), you can map Revit text fonts to specific DGN text fonts as needed.
By default, all the Revit fonts listed in the mapping table have a value of {Automatically map font} in the Text Fonts in DGN column, which means the Revit font will be maintained in the exported file. If you want to map a Revit font to a specific DGN text font, click the value for that font in the Text Fonts in DGN column, and then select the desired font from the drop-down list.
You can click Reset All to change all the DGN font values in the table back to {Automatically map font}. Alternatively, you can multi-select rows and click {Automatically map font}.