• Install VPK
• Copy diabdat.mpq from your CD or GoG installation (or extract it from the GoG installer) to the ux0:/data/diasurgical/devilution/; make sure it is all lowercase.

cd build
cmake -DCMAKE_BUILD_TYPE=Release -DVITA=1 ..
make

• Not supported yet

• Left analog or D-Pad: move hero
• ○: attack nearby enemies, talk to townspeople and merchants, pickup/place items in the inventory, OK while in main menu
• ×: select spell, back while in menus
• △: pickup items, open nearby chests and doors, use item in the inventory
• □: cast spell, delete character while in main menu
• L1: use health item from belt
• R1: use mana potion from belt
• Left back touch panel: character sheet (alt: Start + ←)
• Right back touch panel: inventory (alt: Start + →)
• Start + ↓: toggle automap
• Start + Select: game menu (alt: Start + ↑)
• Select + ×/○/□/△: Spell hotkeys
• Right analog: move automap or simulate mouse
• Select + L1: left mouse click
• Select + R1: right mouse click
• Start + □: quest log
• Start + △: spell book

There's special vita section in diablo.ini file, that allows you to adjust controls:

[vita]
dpad_hotkeys=0
switch_potions_and_clicks=0
back_touch=0
gamepad_mapping=y:b0,b:b1,a:b2,x:b3,leftshoulder:b4,rightshoulder:b5,dpdown:b6,dpleft:b7,dpup:b8,dpright:b9,back:b10,start:b11,leftx:a0,lefty:a1,rightx:a2,righty:a3,

• dpad_hotkeys: dpad works as hotkeys without holding Start button
• switch_potions_and_clicks: L1/R1 works as left/right mouse clicks by debault, and as health/mana potion while holding Select
• gamepad_mapping: allows you to remap controls. It uses https://github.com/gabomdq/SDL_GameControllerDB syntax (but without controller GUID/Name)
• back_touch: enable/disable back touch mapping to L2/R2