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+++ b/doc/sponsoring.md
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+# Sponsoring
+
+<!-- This SVG file can be opened and edited using draw.io -->
+![Sponsoring flow](./sponsoring-flow.svg)
+
+## Implementation
+
+If you need to add sponsoring for pallet call, you should implement `SponsorshipHandler<AccountId, Call, ()>`
+
+If you need to add sponsoring for EVM contract call, you should implement `SponsorshipHandler<H160, (H160, Vec<u8>), CallContext>`
+
+For both examples, you can take a look at `UniqueSponsorshipHandler` struct inside of common runtime
+
+## EVM bridging
+
+In case if Ethereum call is being called using substrate `evm.call` extrinsic, `BridgeSponsorshipHandler` is used to convert between two different `SponsorshipHandler` types