FSRTL.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the FSRTL.H header at

d:\th\minkernel\ntos\inc

and draws from it the following type definitions:

Line Number Type Remarks
353 struct _ECP_LIST line 1669 in NTOSIFS.H
700 struct _NONOPAQUE_OPLOCK  
844 struct _WAITING_IRP  
909 struct _RH_OP_CONTEXT  
969 struct _DELAY_ACK_FO  

The header FSRTL.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).