This is typical code for search ReadSDCard function (called from Mount_FileSystem, example for a710):
ROM:FFC5FCD4 sub_FFC5FCD4 ; CODE XREF: Mount_FileSystem+10p
ROM:FFC5FCD4 ; sub_FFC603F8+2Cp
ROM:FFC5FCD4 LDR R3, =0x2748 ; Load from Memory
ROM:FFC5FCD8 LDR R2, [R3] ; Load from Memory
ROM:FFC5FCDC CMP R2, #0 ; Set cond. codes on Op1 - Op2
ROM:FFC5FCE0 MOVNE PC, LR ; Rd = Op2
ROM:FFC5FCE4 CMP R0, #0 ; Set cond. codes on Op1 - Op2
ROM:FFC5FCE8 LDR R1, =0x2C4A8 ; Load from Memory
ROM:FFC5FCEC MOVNE PC, LR ; Rd = Op2
ROM:FFC5FCF0 LDR R3, =WriteSDCard ; Load from Memory
ROM:FFC5FCF4 LDR R2, =ReadSDCard ; Load from Memory
ROM:FFC5FCF8 STR R3, [R1,#0x50] ; Store to Memory
ROM:FFC5FCFC MOV R3, #3 ; Rd = Op2
ROM:FFC5FD00 STR R0, [R1,#0x38] ; Store to Memory
ROM:FFC5FD04 STR R3, [R1,#0x3C] ; Store to Memory
ROM:FFC5FD08 STR R2, [R1,#0x4C] ; Store to Memory
ROM:FFC5FD0C STR R0, [R1,#0x34] ; Store to Memory
ROM:FFC5FD10 MOV PC, LR ; Rd = Op2