Thanks for your reply.
The reason I asked this question is the Chinese scholar-monk, Ven. YinShun in his works suggests that Saṃyukta-āgama/Saṃyutta-nikāya is the foundation of both the four āgamas/nikāyas, and the Mahayana Madhyamaka and Yogācāra’s essential teachings.
Cf.: Ven. Yinshun: Samyutta/Samyukta Buddhism