react native scroll to top function componet
export const Parent : FC<ParentProps> = props => {
    const scrollRef = useRef<ScrollView>();
    const onFabPress = () => {
        scrollRef.current?.scrollTo({
            y : 0,
            animated : true
        });
    }
    return (
        <View>
            <ScrollView ref={scrollRef}>
                {/* Your content here */}
            </ScrollView>
            <FloatingButton onPress={onFabPress} />
        </View>  
    );
}
export const FloatingButton : FC<FloatingButtonProps> = props => {
    const { onPress } = props;
    const onFabPress = () => {
        // Do whatever logic you need to
        // ...
        onPress();
    }
    return (
        <Fab position="bottomRight" onPress={onFabPress}>
            <Icon name="arrow-round-up" />
        </Fab>
    );
}
if you are using flatlist 
    const scrollRef = useRef<Flatlist>();
    const onFabPress = () => {
        scrollRef.current?.scrollToOffset({
            y : 0,
            animated : true
        });
    }
    
    
scrollToOffset is flatlist fucntion
