ir_rule.xml

<?xml version="1.0"?>
<odoo>
    <data noupdate="1">
        <record model="ir.rule" id="res_partner_portal_holiday_rule">
            <field name="name">res_partner: portal holiday: read access on manager partner</field>
            <field name="model_id" ref="base.model_res_partner"/>
            <field name="domain_force">[('id', 'child_of', user.employee_parent_id.related_contact_ids.ids)]</field>
            <field name="groups" eval="[Command.link(ref('portal_holidays.group_portal_backend_holiday'))]"/>
            <field name="perm_create" eval="False"/>
            <field name="perm_unlink" eval="False"/>
            <field name="perm_write" eval="False"/>
        </record>
    </data>
</odoo>