Vaishnava Samhita. Narayana Muni Charitam. Vol III Book VI Chp 21 Shloka 2

वदन्ति योगिनश्चान्ये नानानियमसंयुताः  |
ध्यानयोगञ्च साष्टाङ्गं पराभक्तिरिति स्फुटम् ||

Some yogis, who strictly follow the rules and regulations, call only the eight fold yogic path as bhakti.