Merge #17350: doc: Add developer documentation to isminetype

40f05647ee doc: Add developer documentation to isminetype (HAOYUatHZ)

Pull request description:

  Closes: https://github.com/bitcoin/bitcoin/issues/17217

ACKs for top commit:
  meshcollider:
    utACK 40f05647ee

Tree-SHA512: 156ff3bc02613d65aed5fcf50250ec3f3365b6c83c810763673ecfdd081a1310e5235be05f0c782638f191be61ad0028511392c40e4106a56eb1c6a3a8ab73b9

src/wallet/ismine.h

@@ -14,7 +14,27 @@
 class CWallet;
 class CScript;
 
-/** IsMine() return codes */
+/**
+ * IsMine() return codes, which depend on ScriptPubKeyMan implementation.
+ * Not every ScriptPubKeyMan covers all types, please refer to
+ * https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.21.0.md#ismine-semantics
+ * for better understanding.
+ *
+ * For LegacyScriptPubKeyMan,
+ * ISMINE_NO: the scriptPubKey is not in the wallet;
+ * ISMINE_WATCH_ONLY: the scriptPubKey has been imported into the wallet;
+ * ISMINE_SPENDABLE: the scriptPubKey corresponds to an address owned by the wallet user (can spend with the private key);
+ * ISMINE_USED: the scriptPubKey corresponds to a used address owned by the wallet user;
+ * ISMINE_ALL: all ISMINE flags except for USED;
+ * ISMINE_ALL_USED: all ISMINE flags including USED;
+ * ISMINE_ENUM_ELEMENTS: the number of isminetype enum elements.
+ *
+ * For DescriptorScriptPubKeyMan and future ScriptPubKeyMan,
+ * ISMINE_NO: the scriptPubKey is not in the wallet;
+ * ISMINE_SPENDABLE: the scriptPubKey matches a scriptPubKey in the wallet.
+ * ISMINE_USED: the scriptPubKey corresponds to a used address owned by the wallet user.
+ *
+ */
 enum isminetype : unsigned int
 {
     ISMINE_NO         = 0,