Finally found it
http://www.quintillion.co.jp/3GPP/Specs/25123-910.pdf (Section 5.2) and http://www.arib.or.jp/english/html/overview/doc/STD-T63v9_40/5_Appendix/R99/25/25133-3m0.pdf (Section 5.3)
Handover between FD and TDD is considered as interfreq handover. See 3GPP 36.133 (RRC), 36.410 (S1 Procedures), 36.420 (X2 Procedures) to understand the mobility completely.
Is it possible to have seamless handover between two mode of LTE i.e. TDD LTE and FDD LTE assuming that the UE supports LTE TDD and LTE FDD both. If yes then how will it happen?