scroll-top-popup-on-submit.php

<?php
add_action( 'wp_footer', 'hoc_popup_reg_form_check', 1000 );
function pum14_popup_reg_form_check() {
	if ( isset( $_POST['form_id'] ) && $_POST['form_id'] == 'my_form' ) {
		?>
		<script type="text/javascript">
			jQuery('#pum-123').animate({'scrollTop': 0}, 1000);
		</script>
		<?php
	}
}