I've composed the component below, and I need to apply a type for the custom iconFontSize prop. How can I do this?
import { SvgIconComponent } from '@mui/icons-material'
import { Typography, TypographyProps} from '@mui/material'

type Props = TypographyProps & {
  Icon: SvgIconComponent
  iconFontSize: /* insert type here! */
}

export const IconTypography = ({
  Icon,
  iconFontSize = 'inherit',
  columnGap = 1,
  children,
  ...props
}: Props) => {
  return (
    <Typography display="flex" alignItems="center" columnGap={columnGap} {...props}>
      <Icon fontSize={iconFontSize} />
      {children}
    </Typography>
  )
}

Thanks in advance!

How to type Material UI Icon's fontSize prop?
You can type iconFontSize as a union type of  'inherit' | 'large' | 'medium' | 'small':
type Props = TypographyProps & {
  Icon: SvgIconComponent
  iconFontSize: "inherit" | "small" | "medium" | "large" 
}

If you want to use the exact type from the MUI type definition file, you can alternatively use:

import { OverridableStringUnion } from '@mui/types';

fontSize?: OverridableStringUnion<
  'inherit' | 'large' | 'medium' | 'small',
  SvgIconPropsSizeOverrides
>;

The OverridableStringUnion type is in turn defined as such:
export type OverridableStringUnion<T extends string | number, U = {}> = GenerateStringUnion<
  Overwrite<Record<T, true>, U>
>;

See the type definition in the MUI docs here: https://mui.com/material-ui/api/svg-icon/
